Spinal stabilization systems and methods

ABSTRACT

A spinal stabilization system may be formed in a patient. In some embodiments, a minimally invasive procedure may be used to form a spinal stabilization system in a patient Bone fastener assemblies may be coupled to vertebrae Each bone fastener assembly may include a bone fastener and a collar. The collar may be rotated and/or angulated relative to the bone fastener. Detachable members may be coupled to the collar to allow for formation of the spinal stabilization system through a small skin incision. The detachable members may allow for alignment of the collars to facilitate insertion of an elongated member in the collars. An elongated member may be positioned in the collars and a closure member may be used to secure the elongated member to the collars.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.11/764,642, filed on Jun. 18, 2007, which is a continuation of U.S.patent application Ser. No. 10/697,793, now U.S. Pat. No. 7,250,052,filed on Oct. 30, 2003, which claims priority to U.S. ProvisionalApplication No. 60/471,254 filed May 16, 2003, which claims priority toU.S. Provisional Application No. 60/466,091 filed Apr. 28, 2003; whichclaims priority to U.S. Provisional Application No. 60/422,455 filedOct. 30, 2002, the entire disclosure of which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention generally relates to spinal stabilization systemsthat include at least one polyaxial fastener. Embodiments of theinvention relate to spinal stabilization systems that may be insertedinto a patient during a minimally invasive surgical procedure.Embodiments of the invention relate to tools used during a minimallyinvasive surgical procedure. Embodiments of the invention relate tomethods of forming implant system components, methods of formingstabilization systems and components, and methods for performingminimally invasive spinal stabilization procedures.

DESCRIPTION OF RELATED ART

Bone may be subject to degeneration caused by trauma, disease, and/oraging. Degeneration may destabilize bone and affect surroundingstructures. For example, destabilization of a spine may result inalteration of a natural spacing between adjacent vertebrae. Alterationof a natural spacing between adjacent vertebrae may subject nerves thatpass between vertebral bodies to pressure. Pressure applied to thenerves may cause pain and/or nerve damage. Maintaining the naturalspacing between vertebrae may reduce pressure applied to nerves thatpass between vertebral bodies. A spinal stabilization procedure may beused to maintain the natural spacing between vertebrae and promotespinal stability.

Spinal stabilization may involve accessing a portion of the spinethrough soft tissue. Conventional stabilization systems may require alarge incision and/or multiple incisions in the soft tissue to provideaccess to a portion of the spine to be stabilized. Conventionalprocedures may result in trauma to the soft tissue, for example, due tomuscle stripping.

Spinal stabilization systems for a lumbar region of the spine may beinserted during a spinal stabilization procedure using a posteriorspinal approach Conventional systems and methods for posterolateralspinal fusion may involve dissecting and retracting soft tissueproximate the surgical site. Dissection and retraction of soft tissuemay cause trauma to the soft tissue, and extend recovery time. Minimallyinvasive procedures and systems may reduce recovery time as well astrauma to the soft tissue surrounding a stabilization site.

U.S. Pat. No. 6,530,929 to Justis et al. (hereinafter “Justis”), whichis incorporated by reference as if fully disclosed herein, describesminimally invasive techniques and instruments for stabilizing a bonystructure in an animal subject. Justis provides a method for using aninstrument to connect at least two bone anchors with a connectingelement. The instrument is secured to the anchors and manipulated toplace the connecting element in a position more proximate the anchors.

SUMMARY

A spinal stabilization system may be installed in a patient to stabilizea portion of a spine. A spinal stabilization system may be installedusing a minimally invasive procedure. An instrumentation kit may provideinstruments and spinal stabilization system components necessary forforming a spinal stabilization system in a patient.

A spinal stabilization system may be used to achieve rigid pediclefixation while minimizing the amount of damage to surrounding tissue. Insome embodiments, a spinal stabilization system may be used to providestability to two or more vertebrae. A spinal stabilization system mayinclude an elongated member, two or more bone fastener assemblies,and/or a closure member. The bone fastener assembly may include, but isnot limited to, a bone fastener and a collar. A first portion of thebone fastener may couple to a portion of the spine during use. A firstportion of a collar may couple to a second portion of the bone fastener.A second portion of the collar may couple to an elongated member duringuse. In some embodiments, an orientation of the bone fastener may beindependent of the orientation of the collar for a bone fastenerassembly. After the bone fastener is placed in a vertebral body, thecollar coupled to the bone fastener may be positioned so that theelongated member can be positioned in the collar and in at least oneother collar that is coupled to another vertebral body by a bonefastener.

In an embodiment, a bone fastener assembly may include a bone fastener,a ring, and a collar. The ring may be positioned in the collar. Removalof the ring from the collar may be inhibited. A bone fastener may bepositioned in the ring through a lower opening in the ring and in thecollar. Splines of the bone fastener may be aligned with seats in thering. The splines may be forced into the seats to couple the ring to thebone fastener. Separation of the ring from the bone fastener may beinhibited after the bone fastener is forced into the seats. The ring mayangulate within the collar (i.e., the bone fastener may move relative tothe collar within a defined range of motion).

In an embodiment, a collar may include, but is not limited to, arms anda body. Arms and body of a collar may form a slot to receive anelongated member. When the elongated member is positioned in the collar,a portion of the elongated member may be coupled to a head of a bonefastener of the bone fastener assembly.

Inner surfaces of the arms of a bone fastener assembly collar mayinclude a modified thread. The modified thread may engage acomplementary modified thread of a closure member. A closure member maysecure an elongated member to a bone fastener assembly. In someembodiments, a range of motion of a collar relative to a bone fastenermay be skewed from a conical range of motion relative to a longitudinalcenter axis of the collar. The skew may be used to accommodate lordoticalignment and/or pedicle angle shift in adjacent vertebrae.

Different instruments may be used to form a spinal stabilization systemin a patient using a minimally invasive procedure. The instruments mayinclude, but are not limited to, positioning needles, guide wires,sleeves, bone fastener driver, mallets, tissue wedges, tissueretractors, tissue dilators, bone awls, taps, and an elongated memberlength estimator. An instrumentation kit may include, but is not limitedto, two or more detachable members (e.g., sleeves), a tissue wedge, anelongated member positioner, a counter torque wrench, an estimatingtool, a seater, closure member driver, and/or combinations thereof.

Detachable members may be used during installation of one vertebrallevel stabilization systems at each of the two vertebrae to bestabilized. In an embodiment, a detachable member may be coupled to acollar of a bone fastener assembly. A detachable member may includechannels to allow movable members to advance and/or retract relative tothe detachable member. In certain embodiments, movable members may bepositioned through other portions of a detachable member. Movablemembers may couple to a bone fastener assembly collar. The movablemembers may inhibit translational and/or rotational movement of thecollar relative to the detachable member.

An estimating tool may be used prior to insertion of an elongated memberinto bone fastener assemblies to estimate a desired length of theelongated member. The estimating tool may include arms. The arms may bepositioned down detachable members to rest on top of collars or bonefasteners of bone fastener assemblies that are coupled to vertebralbodies. The arms of the estimating tool may be expanded to contact innersurfaces of the detachable members. When the ends of the arms contactthe inner surfaces of the detachable members at the bone fastenerassemblies, the estimating tool may be withdrawn from the detachablemembers. The arms may compress during removal, but will spring back tothe measured distance between the detachable members adjacent thecollar. The distance between the arms may be measured using a scale toprovide an estimate of the appropriate elongated member length. Someadditional length may be added to the estimated value to account forcontouring of the elongated member and/or to allow the elongated memberto extend beyond an end of at least two collars

A tissue wedge may be used to form a plane between a first vertebra anda second vertebra during a minimally invasive procedure. The plane mayaccept an elongated member. In an embodiment, a tissue wedge may includea handle portion and a blunted blade. In some embodiments, the blade maybe a double-wedged blade. One edge of the blade may include a hookedportion. The hooked portion may include a cutting edge for severingfascia. The hooked portion may cut fascia positioned in the hookedportion when the tissue wedge is drawn upwards.

In some embodiments, an elongated member positioner may be used to guidean elongated member through detachable members and position theelongated member in collars proximate pedicles of vertebrae. In anembodiment, an elongated member positioner may include a body and aplunger. The body may include a passageway, a handle portion, and anengaging portion. The plunger may contact the elongated member in theengaging portion. In some cases, pressure supplied to an elongatedmember with an elongated member positioner may not be sufficient to seatthe elongated member in collars of bone fastener assemblies. When theelongated member positioner cannot place the elongated member in thecollars, a seater may be used to place the elongated member in thecollars. The seater may include a handle portion. A grooved portion ofthe seater may be used to push the elongated member downwards into thecollars.

In an embodiment, a closure member driver may position a closure memberin a collar coupled to a bone fastener. The closure member driver mayinclude a handle, an elongated portion, and a coupling portion.

In certain embodiments, a detachable member may be held with a countertorque wrench to inhibit injury to the patient as the tool portion of asecured closure member is sheared off. In some embodiments, a countertorque wrench may include a handle portion and a sleeve portion. Adistal end of the sleeve portion may engage an elongated member.

In an embodiment, a method for inserting a stabilization system in aspine may involve determining one or more vertebrae of the spine to betargeted for stabilization, making an incision in the skin, inserting aspinal stabilization system, and closing the incision in the skin.

During some surgical procedures, images of a patient may be taken toassist in determining target locations for insertion of bone fastenerassemblies in vertebrae to be stabilized. A marking or markings may bemade on the patient to indicate the target locations. An incision may bemade in the patient's skin between the target locations. In someembodiments, the incision may be enlarged after insertion of a firstbone fastener assembly. The targeting needle may be inserted into afirst pedicle. Imaging may be used to monitor orientation and depth ofthe targeting needle during insertion.

After insertion of the targeting needle, a guide wire may be insertedthrough a hollow shaft of the targeting needle into the first pedicle.The targeting needle may be removed from the patient. A first bonefastener assembly coupled to a first detachable member may be insertedinto the first pedicle.

A plane may be created in soft tissue between the first bone fastenerassembly and a second pedicle. The plane may be formed without severingmuscle tissue. If needed, fascia may be cut to facilitate formation ofthe plane. After the plane is formed, the targeting needle may beinserted in the first detachable member. A distal end of the targetingneedle may be wanded through the plane and placed at an entry point ofthe second pedicle. The targeting needle may be inserted into the secondpedicle in a desired orientation and to a desired depth. A guide wiremay be inserted through a hollow shaft of the targeting needle into thesecond pedicle. The targeting needle may be removed, and a second bonefastener assembly coupled to a second detachable member may be insertedinto the second pedicle.

An elongated member may be guided down the detachable members. Theelongated member may be seated in the collars. A position of theelongated member in the collars may be confirmed using fluoroscopicimaging. After confirming the position of the elongated member, a firstclosure member coupled to a driver may be advanced down the firstdetachable members. The first closure member may be coupled to the firstcollar. A counter torque wrench may be coupled to the detachable member.A head of the first closure member may be sheared. When the head issheared, enough force is applied to the elongated member by the closuremember to inhibit movement of the elongated member relative to the bonefastener assembly. The driver may be removed from the first closuremember after coupling the first closure member to the first collar. Thesheared off head may be removed from the driver.

The driver may be coupled to a second closure member. A second closuremember coupled to the driver and a counter torque wrench may be usedwhile the head of the closure member is sheared off to form the spinalstabilization system. The detachable members may be removed from thecollars. The incision in the skin may be closed.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will become apparent to thoseskilled in the art with the benefit of the following detaileddescription and upon reference to the accompanying drawings in which:

FIG. 1 depicts a perspective view of an embodiment of a spinalstabilization system.

FIG. 2 depicts a perspective view of an embodiment of a bone fastenerassembly.

FIG. 3 depicts a perspective view of an embodiment of a bone fastener.

FIGS. 4A and 4B depict perspective views of embodiments of bone fastenerassembly rings.

FIG. 5 depicts a perspective view of an embodiment of a bone fastenerassembly collar.

FIG. 6 depicts a cross-sectional view of an embodiment of a bonefastener assembly.

FIG. 7 depicts a perspective view of an embodiment of a bone fastenerassembly.

FIGS. 8A-8C depict schematic views of a method of positioning a ring ina collar of a bone fastener assembly.

FIGS. 9A-9C depict schematic views of a method of positioning a ring ina collar of a bone fastener assembly.

FIGS. 10A and 10B depict schematic views of positioning a bone fastenerin a ring and collar to form a bone fastener assembly.

FIG. 11 depicts a front view of an embodiment of a bone fastenerassembly with a collar that allows for angulation of a bone fastenerrelative to the collar in a conical range of motion that is symmetricalrelative to an axis that passes through a central axis of the collar anda central axis of a bone fastener.

FIG. 12A depicts a front view of an embodiment of a bone fastenerassembly with a collar that allows for angulation of a bone fastenerrelative to the collar in a conical range of motion that is notsymmetrical relative to an axis that passes through a central axis ofthe collar and a central axis of a bone fastener. The collar allowsadditional lateral bias relative to a non-biased collar.

FIG. 12B depicts a side view of an embodiment of a bone fastenerassembly with a collar that allows for angulation of a bone fastenerrelative to the collar in a conical range of motion that is notsymmetrical relative to an axis that passes through a central axis ofthe collar and a central axis of a bone fastener. The collar allowsadditional caudal or cephalid bias relative to a non-biased collar.

FIG. 13A depicts a schematic side view representation of embodiments ofbone fastener assemblies positioned in vertebrae.

FIG. 13B depicts a schematic top view representation of an embodiment ofa single-level spinal stabilization system.

FIG. 14 depicts a perspective view of an embodiment of a closure member.

FIG. 15 depicts a cross-sectional representation of the closure membertaken substantially along plane 15-15 indicated in FIG. 14.

FIG. 16 depicts a perspective view of an embodiment of a portion of aspinal stabilization system.

FIG. 17A depicts a cross-sectional representation of an embodiment of aspinal stabilization system.

FIG. 17B depicts a detailed view of a portion of FIG. 17A.

FIG. 18A depicts a cross-sectional representation of an embodiment of aspinal stabilization system.

FIG. 18B depicts a detailed view of a portion of FIG. 18A.

FIG. 19 depicts a perspective view of an embodiment of a targetingneedle.

FIG. 20 depicts a perspective view of an outer housing of a targetingneedle.

FIG. 21 depicts a perspective view of an embodiment of a member of atargeting needle.

FIG. 22 depicts a perspective view of an embodiment of a guide wire.

FIG. 23 depicts a perspective view of an embodiment of a guide wire.

FIG. 24 depicts a perspective view of an embodiment of a bone awl.

FIG. 25 depicts a perspective view of an embodiment of a bone tap.

FIG. 26 depicts a perspective view of an embodiment of a multi-channelsleeve.

FIG. 27 depicts a top view of an embodiment of a multi-channel sleevewith a bone fastener assembly coupled to the sleeve.

FIG. 28 depicts a cross-sectional representation of a portion of thesleeve with the bone fastener assembly taken substantially along line28-28 of FIG. 27.

FIG. 29 depicts a cross-sectional representation of a portion of thesleeve with the bone fastener assembly taken substantially along line29-29 of FIG. 27.

FIG. 30 depicts a perspective view of an embodiment of a single-channelsleeve.

FIG. 31 depicts a perspective view of an embodiment of a sleeve duringconnection of the sleeve to a collar of a bone fastener assembly.

FIG. 31A depicts a detailed view of a portion of FIG. 31.

FIG. 32 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 33 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 34 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 35 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 36 depicts top view representation of an embodiment of a collar.

FIG. 37 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to an embodiment of a collar of a bonefastener assembly, such as the collar depicted in FIG. 36.

FIG. 38 depicts a top view representation of an embodiment of a collar.

FIG. 39 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to an embodiment of a collar of a bonefastener assembly, such as the collar depicted in FIG. 38.

FIG. 40 depicts a partial cross-sectional view of an embodiment of asleeve with an inner sleeve.

FIG. 41 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 42 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 43 depicts a partial cross-sectional representation of anembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 44 depicts a cross-sectional representation of an embodiment of ahinged sleeve coupled to a collar of a bone fastener assembly.

FIG. 45 depicts a cross-sectional representation of an embodiment of ahinged sleeve coupled to a collar of a bone fastener assembly.

FIG. 46 depicts a schematic representation of sleeve embodiments coupledto collars of a spinal stabilization system.

FIG. 47 depicts a schematic representation of sleeve embodiments withconnections that allow relative movement of portions of a sleeve.

FIG. 48 depicts a perspective view of an embodiment of sleeves coupledto bone fastener assemblies.

FIG. 49 depicts a perspective view of an embodiment of sleeves that arecoupled to bone fastener assemblies.

FIG. 50 depicts a schematic view of sleeve embodiments that are coupledto an embodiment of a frame.

FIG. 51 depicts a perspective view of an embodiment of a driver coupledto a bone fastener and a sleeve.

FIG. 52 depicts a partial cross-sectional view of an embodiment of abone fastener and collar coupled to a driver positioned in a dilator.

FIG. 53 depicts a perspective view of an embodiment of a tissue wedge.

FIG. 54 depicts a perspective view of an embodiment of an estimatingtool.

FIG. 55 depicts a perspective view of an embodiment of an estimatingtool.

FIG. 56 depicts a perspective view of an embodiment of an estimatingtool.

FIG. 57 depicts a perspective view of a tool designed to position anelongated member proximate vertebrae.

FIG. 58 depicts a perspective view of a seater for placing an elongatedmember proximate vertebrae.

FIGS. 59A and 59B depict perspective views of a tool designed toposition a closure member in a collar coupled to a bone fastener.

FIGS. 60A and 60B depict perspective views of a tool designed toposition a closure member in a collar coupled to a bone fastener.

FIG. 61 depicts an embodiment of a counter torque wrench coupled to asleeve.

FIG. 62 depicts an embodiment of a counter torque wrench.

FIG. 63 depicts a schematic view of the counter torque wrench shown inFIG. 62 coupled to an elongated member.

FIGS. 64A-64E depict schematic views of guide wire placement during aminimally invasive spinal stabilization procedure.

FIGS. 65A-65D depict schematic views of tissue dilation during aminimally invasive spinal stabilization procedure.

FIGS. 66A-66F depict schematic views of vertebra preparation forreceiving a bone fastener assembly during a minimally invasive spinalstabilization procedure.

FIGS. 67A-67D depict schematic views of insertion of a sleeve and bonefastener assembly during a minimally invasive spinal stabilizationprocedure.

FIGS. 68A-68D depict schematic views of tissue plane creation during aminimally invasive spinal stabilization procedure.

FIG. 69 depicts an embodiment of a tissue wedge.

FIGS. 70A-70D depict schematic views of placement of a sleeve and a bonefastener assembly in second vertebra during a minimally invasive spinalstabilization procedure.

FIG. 71 depicts a tissue plane between adjacent vertebrae with anchoredsleeves crossing at the surface of the skin.

FIG. 72 depicts an embodiment of an elongated member.

FIG. 73 depicts an embodiment of an elongated member.

FIG. 74 depicts an embodiment of an elongated member.

FIG. 75 depicts an embodiment of an elongated member.

FIGS. 76A-76D depict schematic views of elongated member placementduring a minimally invasive spinal stabilization.

FIG. 77 depicts a perspective view of a distal portion of a two-prongeddriver.

FIGS. 78A-78D depict schematic views of a sleeve removal during aminimally invasive spinal stabilization procedure.

FIGS. 79A-79E depict schematic views of elongated member placement insleeves for a multi-level spinal stabilization system.

FIGS. 80A-80C depict schematic views of bone fastener assemblies coupledto sleeves.

FIG. 81 depicts a perspective view of a bone fastener used in aninvasive procedure.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Thedrawings may not be to scale. It should be understood that the drawingsand detailed description thereto are not intended to limit the inventionto the particular form disclosed, but on the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION

A spinal stabilization system may be installed in a patient to stabilizea portion of a spine. Spinal stabilization may be used, but is notlimited to use, in patients having degenerative disc disease, spinalstenosis, spondylolisthesis, pseudoarthrosis, and/or spinal deformities;in patients having fracture or other vertebral trauma; and in patientsafter tumor resection. A spinal stabilization system may be installedusing a minimally invasive procedure. An instrumentation set may includeinstruments and spinal stabilization system components for forming aspinal stabilization system in a patient.

A minimally invasive procedure may be used to limit an amount of traumato soft tissue surrounding vertebrae that are to be stabilized. In someembodiments, the natural flexibility of skin and soft tissue may be usedto limit the length and/or depth of an incision or incisions neededduring the stabilization procedure. Minimally invasive procedures mayprovide limited direct visibility in vivo. Forming a spinalstabilization system using a minimally invasive procedure may includeusing tools to position system components in the body.

A minimally invasive procedure may be performed after installation ofone or more spinal implants in a patient. The spinal implant or spinalimplants may be inserted using an anterior procedure and/or a lateralprocedure. The patient may be turned and a minimally invasive proceduremay be used to install a posterior spinal stabilization system. Aminimally invasive procedure for stabilizing the spine may be performedwithout prior insertion of one or more spinal implants in some patients.In some patients, a minimally invasive procedure may be used to installa spinal stabilization system after one or more spinal implants areinserted using a posterior spinal approach.

A spinal stabilization system may be used to achieve rigid pediclefixation while minimizing the amount of damage to surrounding tissue. Insome embodiments, a spinal stabilization system may be used to providestability to two adjacent vertebrae (i.e., one vertebral level). Aspinal stabilization system may include two bone fastener assemblies.One bone fastener assembly may be positioned in each of the vertebrae tobe stabilized. An elongated member may be coupled and secured to thebone fastener assemblies. As used herein, “coupled” components maydirectly contact each other or may be separated by one or moreintervening members. In some embodiments, a single spinal stabilizationsystem may be installed in a patient. Such a system may be referred toas a unilateral, single-level stabilization system or a single-level,two-point stabilization system. In some embodiments, two spinalstabilization systems may be installed in a patient on opposite sides ofa spine. Such a system may be referred to as a bilateral, single-levelstabilization system or a single-level, four-point stabilization system.

In some embodiments, a spinal stabilization system may provide stabilityto three or more vertebrae (i.e., two or more vertebral levels). In atwo vertebral level spinal stabilization system, the spinalstabilization system may include three bone fastener assemblies. Onebone fastener assembly may be positioned in each of the vertebrae to bestabilized. An elongated member may be coupled and secured to the threebone fastener assemblies. In some embodiments, a single two-level spinalstabilization system may be installed in a patient. Such a system may bereferred to as a unilateral, two-level stabilization system or atwo-level, three-point stabilization system. In some embodiments, twothree-point spinal stabilization systems may be installed in a patienton opposite sides of a spine. Such a system may be referred to as abilateral, two-level stabilization system or a two-level, six-pointstabilization system.

In some embodiments, combination systems may be installed. For example,a two-point stabilization system may be installed on one side of aspine, and a three-point stabilization system may be installed on theopposite side-of the spine. The composite system may be referred to afive-point stabilization system.

Minimally invasive procedures may reduce trauma to soft tissuesurrounding vertebrae that are to be stabilized. Only a small openingmay need to be made in a patient. For example, for a single-levelstabilization procedure on one side of the spine, the surgical proceduremay be performed through a 2 cm to 4 cm incision formed in the skin ofthe patient. In some embodiments, the incision may be above andsubstantially between the vertebrae to be stabilized. In someembodiments, the incision may be above and between the vertebrae to bestabilized. In some embodiments, the incision may be above andsubstantially halfway between the vertebrae to be stabilized. Dilators,a targeting needle, and/or a tissue wedge may be used to provide accessto the vertebrae to be stabilized without the need to form an incisionwith a scalpel through muscle and other tissue between the vertebrae tobe stabilized. A minimally invasive procedure may reduce an amount ofpost-operative pain felt by a patient as compared to invasive spinalstabilization procedures. A minimally invasive procedure may reducerecovery time for the patient as compared to invasive spinal procedures.

Components of spinal stabilization systems may be made of materialsincluding, but not limited to, titanium, titanium alloys, stainlesssteel, ceramics, and/or polymers. Some components of a spinalstabilization system may be autoclaved and/or chemically sterilized.Components that may not be autoclaved and/or chemically sterilized maybe made of sterile materials. Components made of sterile materials maybe placed in working relation to other sterile components duringassembly of a spinal stabilization system.

Spinal stabilization systems may be used to correct problems in lumbar,thoracic, and/or cervical portions of a spine. Various embodiments of aspinal stabilization system may be used from the C1 vertebra to thesacrum. For example, a spinal stabilization system may be implantedposterior to the spine to maintain distraction between adjacentvertebral bodies in a lumbar portion of the spine.

FIG. 1 depicts an embodiment of spinal stabilization system 100 that maybe implanted using a minimally invasive surgical procedure. Spinalstabilization system 100 may include bone fastener assemblies 102,elongated member 104, and/or closure members 106. Other spinalstabilization system embodiments may include, but are not limited to,plates, dumbbell-shaped members, and/or transverse connectors. FIG. 1depicts a spinal stabilization system for one vertebral level. In someembodiments, the spinal stabilization system of FIG. 1 may be used as amulti-level spinal stabilization system if one or more vertebrae arelocated between the vertebrae in which bone fastener assemblies 102 areplaced. In other embodiments, multi-level spinal stabilization systemsmay include additional bone fastener assemblies to couple to one or moreother vertebrae.

FIG. 2 depicts a perspective view of bone fastener assembly 102. FIG. 3,FIGS. 4A and 4B, and FIG. 5 depict embodiments of bone fastener assemblycomponents. Components of bone fastener assembly 102 may include, butare not limited to, bone fastener 108 (shown in FIG. 3), ring 110 (shownin FIGS. 4A and 4B), and collar 112 (shown in FIG. 5). Bone fastener 108may couple bone fastener assembly 102 to a vertebra. Ring 110 may bepositioned between a head of bone fastener 108 and collar 112.

FIG. 6 depicts a cross-sectional representation of bone fastener 108,ring 110, and collar 112 of bone fastener assembly 102. Bone fastener108 of bone fastener assembly 102 may include passage 114. Bone fastener108 may be cannulated (i.e., passage 114 may run through the full lengthof the bone fastener). A guide wire may be placed through passage 114 sothat bone fastener 108 may be inserted into a vertebra at a desiredlocation and in a desired angular orientation relative to the vertebrawith limited or no visibility of the vertebra

In some embodiments, a bone fastener assembly may be a fixed anglefastener. FIG. 7 depicts an embodiment of a fixed angle bone fastener.Collar and bone fastener may be formed as a unitary piece of metal. Afixed angle fastener may be positioned as the first bone fastenerassembly inserted into a vertebra.

A bone fastener may be, but is not limited to, a bone screw, a ringshank fastener, a barb, a nail, a brad, or a trocar. Bone fastenersand/or bone fastener assemblies may be provided in various lengths in aninstrumentation set to accommodate variability in vertebral bodies. Forexample, an instrumentation set for stabilizing vertebrae in a lumbarregion of the spine may include bone fastener assemblies with lengthsranging from about 30 mm to about 75 mm in 5 mm increments. A bonefastener assembly may be stamped with indicia (i.e., printing on a sideof the collar). In some embodiments, a bone fastener assembly or a bonefastener may be color-coded to indicate a length of the bone fastener.In certain embodiments, a bone fastener with a 30 mm thread length mayhave a magenta color, a bone fastener with a 35 mm thread length mayhave an orange color, and a bone fastener with a 55 mm thread length mayhave a blue color. Other colors may be used as desired.

Each bone fastener provided in an instrumentation set may havesubstantially the same thread profile and thread pitch. In anembodiment, the thread may have about a 4 mm major diameter and about a2.5 mm minor diameter with a cancellous thread profile. In certainembodiments, the minor diameter of the thread may be in a range fromabout 1.5 mm to about 4 mm or larger. In certain embodiments, the majordiameter of the thread may be in a range from about 3.5 mm to about 6.5mm or larger. Bone fasteners with other thread dimensions and/or threadprofiles may also be used. A thread profile of the bone fasteners mayallow bone purchase to be maximized when the bone fastener is positionedin vertebral bone.

FIG. 3 depicts an embodiment of bone fastener 108. Bone fastener 108 mayinclude shank 116, head 118, and neck 120. Shank 116 may includethreading 122. In some embodiments, threading 122 may includeself-tapping start 124. Self-tapping start 124 may facilitate insertionof bone fastener 108 into vertebral bone.

Head 118 of bone fastener 108 may include various configurations toengage a driver that inserts the bone fastener into a vertebra. In someembodiments, the driver may also be used to remove an installed bonefastener from a vertebra. In some embodiments, head 118 may include oneor more tool portions 126. Tool portions 126 may be recesses and/orprotrusions designed to engage a portion of the driver. In someembodiments, bone fastener 108 may be cannulated for use in a minimallyinvasive procedure.

Head 118 of bone fastener 108 may include one or more splines 128, asdepicted in FIG. 3. In some head embodiments, head 118 may include threesplines. Splines 128 may be equally spaced circumferentially around head118 of bone fastener 108. In some head embodiments, splines 128 may bespaced at unequal distances circumferentially around head 118. Splines128 may include various surface configurations and/or texturing toenhance coupling of bone fastener 108 with a ring of a bone fastenerassembly. In some embodiments, sides of the splines may be tapered sothat the splines form a dovetail connection with a ring. In someembodiments, spline width may be tapered so that a good interferenceconnection is established when the bone screw is coupled to a ring.Splines 128 may include one or more projections 130 to facilitatecoupling bone fastener 108 with an inner surface of a ring. In someembodiments, projections 130 may be positioned on a lower portion ofsplines 128. In some embodiments, the splines may include recessedsurfaces that accept projections extending from surfaces of the ring.

Neck 120 of bone fastener 108 may have a smaller diameter than adjacentportions of head 118 and shank 116. The diameter of neck 120 may fix themaximum angle that the collar of the bone fastener assembly can berotated relative to bone fastener 108. In some embodiments, neck 120 maybe sized to allow up to about 40.degree. or more of angulation of thecollar relative to the bone fastener. In some embodiments, the neck maybe sized to allow up to about 30.degree. of angulation of the collarrelative to the bone fastener. In some embodiments, the neck may besized to allow up to about 20.degree. of angulation of the collarrelative to the bone fastener

FIGS. 4A and 4B depict perspective views of embodiments of ring 110.Outer surface 132 of ring 110 may have a contour that substantiallycomplements a contour of an inner surface of a collar in which the ringresides. A contour of the outer surface of the ring may be a sphericalportion. When the ring is positioned in the collar, the complementaryshape of the ring outer surface and the inner surface of the collar thatcontacts the ring allows angulation of the collar relative to a bonefastener coupled to the ring. The contour of the outer surface of thering and the inner surface of the collar may inhibit removal of the ringfrom the collar after insertion of the ring into the collar.

Outer surface 132 of ring 110 may have a smooth finish. In someembodiments, outer surface 132 may be surface treated or includecoatings and/or coverings. Surface treatments, coatings, and/orcoverings may be used to adjust frictional and/or wear properties of theouter surface of the ring. In some embodiments, a portion of the outersurface of the ring may be shaped and/or textured to limit a range ofmotion of the collar relative to a bone fastener of a bone fastenerassembly.

An inner surface of ring 110 may include one or more grooves 134 and/orone or more seats 136. Seats 136 may be circumferentially offset fromgrooves 134. Grooves 134 may be sized to allow passage of splines of abone fastener (e.g., splines 128 shown in FIG. 3) through the ring. Whenthe splines are inserted through grooves 134, the bone fastener may berotated until the splines align with seats 136. The bone fastener may bepulled or driven so that the splines are positioned in seats 136. Insome embodiments, projections (e.g., projections 130 in FIG. 3) may passover ridges 138 of ring 110. Passage of the projections over ridges 138may securely couple the bone fastener to the ring and inhibit separationof the ring from the bone fastener.

In a ring embodiment, a number of grooves 134 and a number of seats 136may equal a number of splines 128 on a head of a bone fastener. Seats136 and grooves 134 may be equally spaced circumferentially around theinner surface of ring 110. In some embodiments, seats 136 may becircumferentially offset about 60.degree. from grooves 134.

In some embodiments, as shown in FIG. 4A, a ring may be a complete ringwithout a split or slots. In some embodiments, a ring may include asplit or slots to facilitate insertion of the ring into a collar. FIG.4B depicts a ring with a split. In some embodiments, a ring with a splitand/or slots may be compressed to ease insertion into a collar. Oncepositioned in the collar, the ring may expand to its originaluncompressed dimensions, thus inhibiting removal from the collar.

As used herein, the term “collar” includes any element that wholly orpartially encloses or receives one or more other elements. A collar mayenclose or receive elements including, but not limited to, a bonefastener, a closure member, a ring, and/or an elongated member. In someembodiments, a collar may couple two or more other elements together(e.g., an elongated member and a bone fastener). A collar may have anyof various physical forms. In some embodiments, a collar may have a “U”shape, however it is to be understood that a collar may also have othershapes.

A collar may be open or closed. A collar having a slot and an open top,such as collar 112 shown in FIG. 2 and in FIG. 5, may be referred to asan “open collar.” A bone fastener assembly that includes an open collarmay be referred to as an “open fastener.” In some embodiments, anelongated member may be top loaded into the open fastener. A closuremember may be coupled to the collar to secure the elongated member tothe open fastener.

A collar that does not include a slot and an open top may be referred toas a “closed collar,” A spinal implant that includes a closed collar maybe referred to as a “closed implant.” A closed collar may include anaperture, bore, or other feature in side surfaces for accommodatingother components of a stabilization system (e.g., an elongated member).A setscrew may be used to securely couple an elongated member to aclosed implant.

Collar 112 may include body 140 and arms 142. Arms 142 may extend frombody 140. Body 140 of collar 112 may be greater in width than a widthacross arms 142 of collar 112 (i.e., body 140 may have a maximumeffective outer diameter greater than a maximum effective outer diameterof arms 142). A reduced width across arms 142 may allow a detachablemember to be coupled to the arms without substantially increasing amaximum effective outer diameter along a length of collar 112. Thus, areduced width across arms 142 may reduce bulk at a surgical site.

A height of body 140 may range from about 3 millimeters (mm) to about 7mm. In an embodiment, a height of body 140 is about 5 mm. Body 140 mayinclude opening 144 in a lower surface of the body. To inhibit passageof a ring from collar 112, opening 144 may be smaller than an outerdiameter of the ring. Inner surface 146 may be machined to complement aportion of an outer surface of a ring that is to be positioned in collar112. Machining of inner surface 146 may enhance retention of a ring incollar 112. Inner surface 146 of body 140 may be complementary in shapeto a portion of outer surface 132 of ring 110 (see FIG. 4) so that thering is able to swivel in the collar. Inner surfaces and/or outersurfaces of collar 112 may be surface treated or include coatings and/orcoverings to modify frictional properties or other properties of thecollar.

Inner surfaces of arms 142 may include modified thread 148. Modifiedthreads 148 may engage complementary modified threads of a closuremember to secure an elongated member to a bone fastener assembly.Modified threads 148 may have a constant pitch or a variable pitch.

A height and a width of arms 142 may vary. Arms 142 may range in heightfrom about 8 mm to about 15 mm. In an embodiment, a height of arms 142is about 11 mm. A width (i.e., effective diameter) of arms 142 may rangefrom about 5 mm to 14 mm. Arms 142 and body 140 may form slot 150. Slot150 may be sized to receive an elongated member. Slot 150 may include,but is not limited to, an elongated opening of constant width, anelongated opening of variable width, a rectangular opening, atrapezoidal opening, a circular opening, a square opening, an ovoidopening, an egg-shaped opening, a tapered opening, and combinationsand/or portions thereof. In some embodiments, a first portion of slot150 may have different dimensions than a second portion of slot 150. Incertain embodiments, a portion of slot 150 in first arm 142 may havedifferent dimensions than a portion of slot 150 in second arm 142. Whenan elongated member is positioned in slot 150, a portion of theelongated member may contact a head of a bone fastener positioned in thecollar.

In an embodiment of a collar, arms 142 of collar 112 may include one ormore openings and/or indentions 152. Indentions 152 may vary in size andshape (e.g., circular, triangular, rectangular). Indentions 152 may beposition markets and/or force application regions for instruments thatperform reduction, compression, or distraction of adjacent vertebrae. Insome embodiments, openings and/or indentions may be positioned in thebody of the collar.

Arms 142 may include ridges or flanges 154. Flange 154 may allow collar112 to be coupled to a detachable member so that translational motion ofthe collar relative to the detachable member is inhibited. Flanges 154may also include notches 156. A movable member of a detachable membermay extend into notch 156. When the movable member is positioned innotch 156, a channel in the detachable member may align with a slot incollar 112. With the movable member positioned in notch 156, rotationalmovement of collar 112 relative to the detachable member may beinhibited.

FIGS. 8A-8C show views of collar 112 and ring 110 during top loadinginsertion of the ring into the collar. Ring 110 may be positioned asshown in FIG. 8A and inserted past arms 142 into body 140. FIG. 8Bdepicts a cross-sectional view of ring 110 and collar 112 afterinsertion of the ring into the collar through slot 150. After insertionof ring 110 into collar 112, the ring may be rotated so that a bonefastener may be positioned through the ring. FIG. 8C depicts across-sectional view of ring 110 and collar 112 after rotation of thering in the collar.

FIGS. 9A-9C show views of collar 112 and ring 110 during bottom loadinginsertion of the ring into the collar. Ring 110 may be positioned asshown in FIG. 9A and inserted into body 140 through an opening in thebottom of collar 112. In some embodiments, ring 110 may be inserted intobody 140 through a groove or a slot in the bottom of collar 112. Incertain embodiments, collar 112 designed for bottom insertion of ring110 may have narrower slot 150 than a collar designed for top insertionof a ring. Collar 112 with narrower slot 150 may allow an elongatedmember with a reduced diameter to be used in a spinal stabilizationsystem. Collar 112 with narrower slot 150 may be used to reduce bulk ata surgical site.

FIG. 9B depicts a cross-sectional view of ring 110 and collar 112 afterinsertion of the ring into the collar through the opening in the bottomof the collar. After insertion of ring 110 into collar 112, the ring maybe rotated so that a bone fastener may be positioned through the ring.Tolerance between an outer surface of ring 110 and an inner surface ofbody 140 shown in FIGS. 8A-8C and 9A-9C may require force to be appliedto the ring to drive the ring into the body. Once ring 110 is positionedin body 140, the ring may expand slightly. In certain embodiments,significant force may be required to remove ring 110 from body 140(i.e., the ring may be substantially unreleasable from the body). Therequired force may inhibit unintentional removal of ring 110 from body140. FIG. 9C depicts a cross-sectional view of ring 110 and collar 112after rotation of the ring in the collar.

FIG. 10A depicts bone fastener 108 before insertion of the bone fastenerinto ring 110 positioned in collar 112. Splines 128 may be aligned withgrooves 134 to allow passage of head 118 through ring 110 and intocollar 112. FIG. 10B depicts bone fastener 108, ring 110, and collar 112after the bone fastener has been rotated and head 118 has been coupledto seats in the ring to form bone fastener assembly 102. Inserting bonefastener 108 through opening 144 in collar 112 (depicted in FIG. 10A)may allow use of bone fasteners that have shanks and/or heads withlarger diameters than can pass through slot 150. Bone fasteners withlarge diameter shanks may form a bone fastener assembly (threaded orotherwise) that securely fastens to vertebral bone during use.

A bone fastener may be rotatably positioned in a collar such that thebone fastener is able to move radially and/or rotationally relative tothe collar (or the collar relative to the bone fastener) within adefined range of motion. The range of motion may be provided within aplane, such as by a hinged connection, or within a three-dimensionalregion, such as by a ball and socket connection. Motion of the bonefastener relative to the collar (or the collar relative to the bonefastener) may be referred to as “angulation” and/or “polyaxialmovement”. FIG. 11 depicts bone fastener assembly 102 with central axis158 of collar 112 aligned with central axis 160 of bone fastener 108.Bone fastener 108 may be angulated in a symmetrical conical range ofmotion characterized by angle .alpha. about the aligned axes. Bonefastener 108 may be constrained from motion outside of limit axis 162 bycontact between neck 120 of bone fastener 108 and collar 112. Alignmentof axis 160 of bone fastener 108 with central axis 158 of collar 112 maybe considered a neutral position relative to the range of motion. Thealignment is a neutral position because bone fastener 108 may beangulated an equal amount in any direction from central axis 158. When adriver is inserted into bone fastener 108, axis 160 of bone fastener 108may be substantially aligned with axis 158 of collar 112 to facilitateinsertion of the bone fastener into a vertebral body.

In certain embodiments, a range of motion of a collar may be skewed froma full conical range of motion relative to aligned central axes of thecollar and a bone fastener coupled to the collar. In some embodiments, adistal end of a collar may be shaped to skew, or bias, the range ofmotion from the range of motion depicted in FIG. 11. FIGS. 12A and 12Bdepict bone fastener assemblies 102 with biased collars 112. Body 140 ofbiased collar 112 may be shaped to restrict relative movement of bonefastener 108 (and/or the collar) to a skewed conical range of motiondefined by limit axes 162. As depicted by limit axes 162 in FIG. 12A, afirst arm 142 of collar 112 may approach bone fastener 108 more closelythan a second arm of the collar. As suggested by limit axes 162 in FIG.12B, a first opening of the slot between arms 142 of collar 112 mayapproach bone fastener 108 more closely than a second opening of theslot.

Other biased collars may be designed to selectively restrict relativemovement of collars and/or bone fasteners. In some embodiments, a biasedcollar may be attached to a detachable member such that a surgeonperforming a minimally invasive procedure may selectively align theportion of the collar with the greater range of motion as needed. Forexample, the collar depicted in FIG. 12B may be coupled to asingle-level (e.g., C-shaped) sleeve so that the side of the collar(i.e., the side of the slot) with a larger range of motion is positionednext to a channel opening of the sleeve.

When a biased collar of a bone fastener assembly is coupled to adetachable member and a drive mechanism is coupled to a bone fastener ofthe bone fastener assembly, central axis 158 of collar 112 may alignwith central axis 160 of bone fastener 108 to facilitate insertion ofthe bone fastener into bone. In some embodiments, the bias of the collarmay be so large that a flexible drive member is needed to drive the bonefastener into bone.

In some embodiments, one or more biased collars may be used in a spinalstabilization system. The spinal stabilization systems may besingle-level systems or multi-level systems. Biased collars may be usedto accommodate the increasing angle of the pedicle corridor for eachlumbar vertebra. The angle may increase by about 5 degrees for eachsuccessive lumbar vertebra. FIGS. 13A and 13B depict a single-levelspinal stabilization system including bone fastener assembly 102Acoupled to pedicle 164A and vertebra 166A and bone fastener assembly102B coupled to pedicle 164B and vertebra 166B.

A bone fastener of bone fastener assembly 102A may engage pedicle 164Aat pedicle angle .phi.A relative to sagittal plane 168. Pedicle angle.phi.A may range between about 13.degree. and about 17.degree. Collar112A of bone fastener assembly 102A may be unbiased. Pedicle angle.phi.B may range between about 18.degree. and about 22.degree. Collar112B may have a bias angle .beta. of about 5.degree. Bone fastenerassembly 102B may engage pedicle 164B at pedicle angle .phi.B. Becausethe bias of collar 112B is approximately equal to the difference betweenthe pedicle angles of the two vertebrae, slots 150A and 150B in bonefastener assemblies 102A and 102B, respectively, may be generallyaligned when both bone fasteners are in neutral positions.

Angulation of either or both collars of the bone fastener assemblies mayallow fine adjustment of engagement angles of the bone fasteners. Inaddition, collar angulation may allow adjustment in the orientation ofbone fasteners in a sagittal plane (i.e., to conform to lordosis of aspine) while still allowing the collars to be easily coupled withelongated member 104. Elongated member 104 may be disposed in slots 150Aand 150B and secured by closure members. In some embodiments, a flexibledriver or a polyaxial driver (e.g., a driver with a universal joint) maybe used to drive the heads of the bone fasteners from a position that isoff-axis from the bone fasteners to reduce the size of an opening of thebody needed to implant the spinal stabilization system.

A closure member may be coupled to a collar of a bone fastener assemblyto fix an elongated member positioned in the collar to the bone fastenerassembly. In some embodiments, a closure member may be cannulated. Incertain embodiments, a closure member may have a solid central core. Aclosure member with a solid central core may allow more contact areabetween the closure member and a driver used to couple the closuremember to the collar. A closure member with a solid central core mayprovide a more secure connection to an elongated member than acannulated closure member by providing contact against the elongatedmember at a central portion of the closure member as well as near anedge of the closure member.

FIG. 1 depicts closure members 106 coupled to bone fastener assemblies102. FIG. 14 depicts closure member 106 prior to insertion of theclosure member into a collar of a bone fastener assembly. Closure member106 may include tool portion 170 and male modified thread 172. Toolportion 170 may couple to a tool that allows closure member 106 to bepositioned in a collar. Tool portion 170 may include variousconfigurations (e.g., threads, hexalobular connections, hexes) forengaging a tool (ergo, a driver). Male modified thread 172 may have ashape that complements the shape of a female modified thread in arms ofa collar (e.g., modified thread 148 depicted in FIG. 5).

FIG. 15 depicts a cross-sectional representation of closure member 106taken substantially along plane 15-15 of FIG. 14. Closure member 106 mayinclude removal openings 174. A drive tool may be inserted into removalopenings 174 to allow removal of closure member 106 after tool portion170 has been sheared oft. Removal openings 174 may include any of avariety of features including, but not limited to, sockets, holes,slots, and/or combinations thereof. In an embodiment, removal openings174 are holes that pass through bottom surface 176 of closure member106.

A bottom surface of a closure member may include structure and/ortexturing that promotes contact between the closure member and anelongated member. A portion of the structure and/or texturing may enterand/or deform an elongated member when the closure member is coupled tothe elongated member. Having a portion of the closure member enterand/or deform the elongated member may couple the elongated member tothe closure member and a bone fastener assembly so that movement of theelongated member relative to the bone fastener assembly is inhibited. Ina closure member embodiment, such as the embodiment depicted in FIG. 15,bottom surface 176 of closure member 106 may include point 178 and rim180. In some embodiments, rim 180 may come to a sharp point. In someembodiments, a height of rim 180 may be less than a height of point 178.In other embodiments, a height of rim 180 may be the same or larger thana height of point 178. In some embodiments, rim 180 may not extendcompletely around the closure member. For example, eight or moreportions of rim 180 may be equally spaced circumferentially aroundclosure member 106. In certain embodiments, a solid central coreincluding point 178 and rim 180 may enhance the ability of closuremember 106 to secure an elongated member in a collar.

FIG. 16 depicts a portion of a spinal stabilization system with closuremember 106 coupled to collar 112 before tool portion 170 is sheared off.Closure member 106 may couple to collar 112 by a variety of systemsincluding, but not limited to, standard threads, modified threads,reverse angle threads, buttress threads, or helical flanges. A buttressthread on a closure member may include a rearward-facing surface that issubstantially perpendicular to the axis of the closure member. Closuremember 106 may be advanced into an opening in a collar to engage aportion of elongated member 104. In some embodiments, closure member 106may inhibit movement of elongated member 104 relative to collar 112.

FIG. 17A depicts a cross-sectional view of closure member 106 coupled tobone fastener assembly 102. Closure member 106 may include male modifiedthread 172. Male modified thread 172 may include male distal surface 182and male proximal surface 184, as shown in FIG. 17B. Collar 112 mayinclude female modified thread 148 on an inside surface of arms 142.Female modified thread 148 may include female proximal surface 186 andfemale distal surface 188. Male proximal surface 184 may couple tofemale distal surface 188 during use. Male proximal surface 184 andfemale distal surface 188 may be load-bearing surfaces. A load mayresult from an upward load on closure member 106, such as a loadresulting when elongated member 104 positioned in a slot of collar 112is secured to bone fastener assembly 102 by closure member 106.

Raised portions 190 and recessed portions 192 may be included on maledistal surface 182 and female proximal surface 186. Cooperating surfaces194 of modified threads 172 and 148 may contact or be proximate to oneanother during use. As used herein, “proximate” means near to or closerto one portion of a component than another portion of a component.Engagement of cooperating surfaces 194 of modified threads 172 and 148during use may inhibit radial expansion of collar 112. Engagement ofcooperating surfaces 194 may inhibit spreading of arms 142 away fromeach other (i.e., inhibit separation of the arms). In some embodiments,cooperating surfaces 194 may be substantially parallel to a central axisof closure member 106. In other embodiments, cooperating surfaces 194may be angled relative to a central axis of closure member 106.

In some embodiments, a proximal surface of a male modified thread mayinclude raised and recessed portions. FIG. 18A depicts a cross-sectionalview of bone fastener assembly 102 coupled to closure member 106 withraised and recessed portions on a proximal surface of male modifiedthread 172. FIG. 18B depicts a cross-sectional view of raised portions190 at male proximal surface 184 of male modified thread 172 and femaledistal surface 188 of female modified thread 148. Male proximal surface184 may include an overall positive slope S such that point A near thetop of male modified thread 172 is distal from point B at the base ofthe male modified thread. Alternatively, male proximal surface 184 mayinclude an overall negative slope or a slope of about zero.

In an embodiment, a bone fastener assembly and a closure member may becoupled with a running fit. A running fit (i.e., a fit in which partsare free to rotate) may result in predictable loading characteristics ofa coupling of a bone fastener assembly and a closure member. Predictableloading characteristics may facilitate use of a closure member with abreak-off portion designed to shear off at a predetermined torque. Arunning fit may also facilitate removal and replacement of closuremembers. In some embodiments, a closure member may include aninterference fit (e.g., crest-to-root radial interference).

In an embodiment, a position (i.e., axial position and angularorientation) of a modified thread of a collar may be controlled, or“timed,” relative to selected surfaces of the collar. For example, amodified thread form may be controlled relative to a top surface of acollar and an angular orientation of the slots of the collar. In someembodiments, positions of engaging structural elements of other couplingsystems (e.g., thread forms) may be controlled.

Controlling a position of a modified thread form may affect a thicknessof a top modified thread portion of a collar. In FIG. 5, top modifiedthread portion 196 is the first modified thread portion to engage aclosure member. In an embodiment, a position of a modified thread formmay be selected such that the thickness of the leading edge of a topmodified thread portion is substantially equal to the full thickness ofthe rest of the modified thread.

Controlling a position of a modified thread form of a collar mayincrease a combined strength of engaged modified thread portions for acollar of a given size (e.g., wall height, modified thread dimensions,and thread pitch). Controlling a position of the modified thread formmay reduce a probability of failure of modified thread portions, andthus reduce a probability of coupling failure between a collar and aclosure member. Controlling the position of a modified thread form in acollar of a bone fastener assembly may increase a combined strength ofengaged collar and closure member modified thread portions such thatfailure of the modified thread portions does not occur prior to theintended shearing off of a tool portion of the closure member. Forexample, a tool portion of a closure member may be designed to shear offat about 90 in-lbs of torque, while the combined modified threadportions may be designed to withstand a torque on the closure member ofat least 120 in-lbs.

If a thickness of a modified thread portion of a given size and profileis reduced below a minimum thickness, the modified thread portion maynot significantly contribute to the holding strength of the modifiedthread of a collar. In an embodiment, a position of a modified threadform of a collar may be controlled such that a thickness of a topmodified thread portion is sufficient for the portion to increase aholding strength of the collar. In one embodiment, a top modified threadportion may have a leading edge thickness of about 0.2 mm.

In an embodiment, a position of a modified thread form of a collar maybe selected to ensure that a closure member engages a selected minimumnumber of modified thread portions on each arm of the collar. In anembodiment, at least two modified thread portions having a fullthickness over width w of a collar arm (shown in FIG. 5) may be engagedby a closure member at each arm. Alternatively, a closure member mayengage parts of three or more modified thread portions on each arm, withthe total width of the portions equal to at least two full-widthportions. Allowances may be made for tolerances in the components (e.g.,diameter of the elongated member) and/or anticipated misalignmentbetween the components, such as misalignment between an elongated memberand a slot. In an embodiment, a substantially equal number of modifiedthread portions in each arm may engage the closure member when anelongated member is coupled to a bone fastener assembly.

Various instruments may be used in a minimally invasive procedure toform a spinal stabilization system in a patient. The instruments mayinclude, but are not limited to, positioning needles, guide wires,dilators, bone awls, bone taps, sleeves, drivers, tissue wedges,elongated member length estimating tools, mallets, tissue retractors,and tissue dilators. The instruments may be provided in aninstrumentation set. The instrumentation set may also include componentsof the spinal stabilization system. The components of the spinalstabilization system may include, but are not limited to, bone fastenerassemblies of various sizes and/or lengths, elongated members, andclosure members.

Instruments used to install a spinal stabilization system may be made ofmaterials including, but not limited to, stainless steel, titanium,titanium alloys, ceramics, and/or polymers. Some instruments may beautoclaved and/or chemically sterilized Some instruments may includecomponents that cannot be autoclaved or chemically sterilized.Components of instruments that cannot be autoclaved or chemicallysterilized may be made of sterile materials. The sterile materials maybe placed in working relation to other parts of the instrument that havebeen sterilized.

A targeting needle may be used to locate an entry point in a vertebralbody for a bone fastener of a bone fastener assembly. In someembodiments, the targeting needle may be a Jamshidi.RTM. bone marrowbiopsy needle. FIG. 19 depicts an embodiment of targeting needle 198.Targeting needle 198 may include outer housing 200 and member 202. FIG.20 depicts an embodiment of outer housing 200. Outer housing 200 mayinclude hollow shaft 204 and handle 206. Scale markings 208 may beprinted, etched, or otherwise placed on hollow shaft 204. Scale markings208 may be used to approximate a length of a bone fastener needed for avertebra. Handle 206 may provide a grip that allows a user to manipulatethe targeting needle. Handle 206 may include threaded portion 210.Threaded portion 210 may couple to threading on a portion of a targetingneedle member to secure the member to outer housing 200.

FIG. 21 depicts an embodiment of member 202 of a targeting needle.Member 202 may include point 212 and cap 214. Point 212 may be placedthrough a hollow shaft of an outer housing of the targeting needle. Cap214 may include threading 216. Member 202 may be rotated relative to theouter housing to couple threading 216 with threading in a handle of theouter housing. In some embodiments, the member may be coupled to theouter housing by another type of connection system (e.g., by placementof a key in a keyway). With member 202 positioned in an outer housing,point 212 may extend from a distal end of a hollow shaft of the outerhousing. Cap 214 may be used as an impact surface for driving thetargeting needle in bone.

FIG. 22 and FIG. 23 depict embodiments of guide wire 218. Guide wire 218may be an 18-gauge K-wire. Guide wire 218 may pass down a shaft of atargeting needle outer housing. A guide wire may be from about 15 cm toabout 65 cm in length. In some embodiments, guide wires provided in aninstrumentation set are about 46 cm in length. The length of guide wire218 may allow a surgeon and/or assistants to hold at least one portionof the guide wire at all times when the guide wire is inserted intovertebral bone, even during insertion, use, and removal of instrumentsalong a length of the guide wire. A guide wire that can be heldcontinuously during a surgical procedure may inhibit removal oradvancement of the guide wire from a desired position during a minimallyinvasive surgical procedure.

As depicted in FIG. 22, a distal end of guide wire 218 may include point220. Point 220 may facilitate insertion of the distal end of guide wire218 into vertebral bone. As depicted in FIG. 23, a distal end of guidewire 218 may not be pointed. A position of an unpointed guide wire inbone may be easier to maintain during a spinal stabilization procedure.

Dilators may be used during a minimally invasive surgical procedure topush aside tissue and create space to access vertebral bone. In someembodiments, four tissue dilators of increasing diameter may be used toestablish sufficient working space to accommodate instruments and spinalstabilization system components. In some embodiments, especially for amid-vertebra or for mid-vertebrae of a multi-level stabilization system,only three dilators may be needed to form sufficient working space.Dilators in an instrumentation set may increase in diameterincrementally by a selected amount. For example, outside diameters ofdilators in an instrumentation set may increase sequentially byincrements of about 0.5 mm.

A bone awl may be used to breach cortical bone of a pedicle. FIG. 24depicts an embodiment of bone awl 222. Bone awl 222 may include handle224, passage 226, and tip 228. Handle 224 may provide a secure grip thatallows a surgeon to breach cortical bone of a pedicle with tip 228. Aguide wire that is inserted in vertebral bone in a desired orientationmay be inserted through passage 226 that extends through bone awl 222.Bone awl 222 may be moved down the guide wire so that tip 228 contactsthe pedicle.

Bone awl 222 may have a length that allows a guide wire positioned invertebral bone to always be held in at least one location when the guidewire is placed through passage 226 in the needle. In some embodiments,handle 224 may be removable from a shaft of bone awl 222 so that theguide wire may always be held during use of the bone awl.

During some surgical procedures downward force and some rotation of thebone awl may be sufficient to breach cortical of a vertebra. During somesurgical procedures, an impact force may be needed for the bone awl tobreach cortical bone. In some embodiments, a guide wire may be removed,the bone awl may be used to breach cortical bone, and the guide wire maybe reinserted. In some embodiments, a small dilator may be placed overthe portion of the guide wire extending from the bone awl so that afirst end of the dilator contacts the bone awl. A mallet or other impactdevice may be used against a second end of the dilator so that the boneawl breaches cortical bone of the vertebra. The dilator may be removedfrom the bone awl and contact with the guide wire may be reestablished.

A bone tap may be used to form a threaded passage of a desired depththrough a pedicle and into a vertebral body. FIG. 25 depicts anembodiment of tap 230. Tap 230 may include passage 232, shaft 234,removable handle 236, flutes 238, and indicia 240. Passage 232 mayextend through a length of shaft 234 and removable handle 236. A guidewire positioned in vertebral bone may be inserted into a distal end ofpassage 232 so that tap 230 can be moved down the guide wire toward thebone.

In an embodiment of tap 230, a proximal portion of shaft 234 may includeat least one flat portion that fits in a mating portion of removablehandle 236. Proximal end of shaft 234 may also include a detentdepression. The flat portion may allow for rotation of shaft 234 whenremovable handle 236 is rotated. An embodiment of removable handle 236may include spring-loaded release 242. When spring-loaded release 242 iscompressed (i.e., drawn upwards), a detent in removable handle 236 maybe movable. When spring-loaded release 242 is not compressed, movementof the detent may be inhibited. When shaft 234 is positioned inremovable handle 236, the detent of the removable handle may bepositioned in the detent depression of shaft 234 to couple the shaft tothe removable handle.

A tap portion of tap 230 may have a known length. As shown in FIG. 25, atap portion of tap 230 may have a length t. In some embodiments, t maybe about 20 mm, about 40 mm, about 60 mm, or greater. For example, t maybe about 45 mm. X-ray monitoring of a depth of a tap portion of knownlength may allow a medical practitioner to assess a depth of a holetapped in a bone. In some embodiments, the hole may be tapped toaccommodate a bone fastener of a desired length. In certain embodiments,a bone fastener may be chosen to accommodate a hole tapped to a desireddepth.

A guide wire positioned in vertebral bone may be held near a top of adilator inserted over the guide wire at a surgical site. A proximal endof the guide wire may be positioned through a distal end of a passage inshaft 234 of tap 230 without a removable handle coupled to the shaft. Aproximal portion of the guide wire may be held when the proximal portionof the guide wire extends beyond the top of shaft 234. A portion of theguide wire may always be held during use of tap 230. Shaft 234 may bemoved down the guide wire until the shaft contacts the vertebral bone.The guide wire may be held near the top of shaft 234 and the guide wiremay be positioned through passage 232 of removable handle 236. When theguide wire extends out of passage 232 through removable handle 236, theguide wire may be held above the removable handle. The handle may becoupled to the shaft using spring-loaded release 242.

A first reading of indicia 240 relative to a proximal end of a dilatormay be taken when a first flute of flutes 238 is located at a pedicle.Tap 230 may be rotated so that flutes 238 form a threaded openingthrough the pedicle and into a vertebral body. Flutes 238 may have adiameter that is about 0.1 mm to about 0.7 mm less than a maximum threadflight of a bone fastener to be positioned in the threaded openingformed by the flutes. In an embodiment, tap may form a thread that isabout 0.5 mm less than a maximum thread flight of a bone fastener to bepositioned in the threaded opening formed by the flutes. A position oftap 230 may be monitored using a fluoroscope. When the threaded openingis formed to a desired depth, a second reading of indicia 240 relativeto the dilator may be taken. A length of a bone fastener to be insertedinto the vertebral body may be estimated by taking the differencebetween the indicia readings.

After a threaded opening is formed to a desired depth, tap 230 may beremoved by rotating the tap until flutes 238 are disengaged fromvertebral bone. Removable handle 236 may be separated from shaft 234,and the removable handle may be removed with the guide wire always heldin at least one location. After removable handle 236 is removed from theguide wire, shaft 234 may be removed with the guide wire always held inat least one location.

A detachable member may be used as a guide to install bone fasteners ofa bone fastener assembly in vertebral bone. A detachable member may becoupled to a collar of a bone fastener assembly. A distal end of adetachable member may be tapered or angled to reduce bulk at a surgicalsite. Instruments may be inserted into the detachable member tomanipulate the bone fastener assembly. Movement of the detachable membermay alter an orientation of a collar relative to a bone fastener of thebone fastener assembly. In some embodiments, a detachable member may beused as a retractor during a spinal stabilization procedure.

A detachable member for a single-level vertebral stabilization systemmay include one or more channels in a wall of the detachable member toallow access to an adjacent vertebra. For some single-level vertebralstabilization procedures, only single-channel detachable members (i.e.,detachable members with a single channel in a wall of the detachablemember) may be used. For other single-level vertebral stabilizationprocedures, one or more multi-channel detachable members (i.e.,detachable members with two or more channels in a wall of the detachablemember) may be used. Channels may provide flexibility to or enhanceflexibility of a multi-channel detachable member. In some embodiments, aproximal portion of a multi-channel detachable member may have a solidcircumference. A region of solid circumference in a multi-channeldetachable member may enhance stability of the multi-channel detachablemember. In some embodiments, a multi-channel detachable member may belonger than a single-channel detachable member.

A detachable member used at a middle vertebra in a multi-levelstabilization procedure may be a multi-channel detachable member.Channels in a multi-channel detachable member may allow access toadjacent vertebrae from a middle vertebra. A detachable member used atan end vertebra of a multi-level stabilization system may be asingle-channel detachable member or a multi-channel detachable member. Asystem for coupling a bone fastener assembly to a multi-channeldetachable member may include a limiter that inhibits spreading of armsof the detachable member to inhibit release of the bone fastenerassembly from the detachable member.

A channel in a wall of a detachable member may allow access to avertebra that is to be stabilized with a spinal stabilization systembeing formed. In some embodiments, a single-channel detachable membermay be coupled to a bone fastener assembly to be inserted into vertebralbone of a first vertebra. The single-channel detachable member may allowaccess to a second vertebra from the first vertebra. In otherembodiments, a multi-channel detachable member may be coupled to a bonefastener assembly to be inserted into vertebral bone of a firstvertebra. The multi-channel detachable member may allow access from thefirst vertebra to adjacent vertebrae.

Instruments may access a bone fastener assembly through a passage in adetachable member. In some embodiments, a channel in a wall of adetachable member may extend a full length of the detachable member. Insome embodiments, especially in embodiments of multi-channel detachablemembers, a channel in a wall of a detachable member may extend only aportion of the length of the detachable member. In some embodiments, achannel in a wall of a detachable member may extend 25%, 50%, 75%, 80%,90%, 95% or more of the length of the detachable member. A channel mayextend to a distal end of a detachable member such that an elongatedmember inserted in the channel may pass from the detachable member intoa slot of a collar of a bone fastener assembly coupled to the detachablemember.

A channel in a detachable member may be any of a variety of shapes. Achannel may have a width that exceeds a width (e.g., a diameter) of anelongated member that is to be inserted in the channel. In someembodiments, a channel may be a linear opening parallel to alongitudinal axis of the detachable member. In some embodiments, achannel may have a non-linear shape including, but not limited to, ahelical pattern, an arc, an “L” shape, or an “S” shape. A non-linearchannel may allow an elongated member to travel along a predeterminedpath. In certain embodiments, adjacent detachable members may includechannels with matching profiles, allowing ends of an elongated member tofollow similar paths down the detachable member channels.

Movable members may extend through portions of a detachable memberproximate a channel in the detachable member. Movable members may engagenotches in a collar to establish a radial orientation of the detachablemember on the collar and/or to inhibit rotation of the collar relativeto the detachable member. A distal end of a movable member may be flat,curved, or angled. In some embodiments, a distal end of a movable membermay be threaded. In other embodiments, a distal end of a movable membermay be a projection that engages an opening in a collar. In someembodiments, an upper surface of a collar and/or a surface of a distalend of a movable member may be textured to inhibit rotation of thecollar relative to the detachable member. In certain embodiments, aproximal end of a movable member may include a tool engaging portion. Atool engaging portion may include, but is not limited to, a hex section,a hexalobular section, a tapered section, a bead, a knot, a keyedopening, a coating, a threading, and/or a roughened surface for engaginga drive that rotates or otherwise displaces the movable member.

A cross section transverse to a longitudinal axis of a detachable membermay have shapes including, but not limited to, circular, ovoid, square,pentagonal, hexagonal, and combinations thereof. In some embodiments, adetachable member may be hollow. In certain embodiments, a thickness ofa hollow detachable member may be uniform. In certain embodiments, athickness of a hollow detachable member may vary along the length of thedetachable member. A detachable member with a passage extendinglongitudinally from a first end of the detachable member to a second endof the detachable member may be referred to as a “sleeve”.

FIG. 26 depicts an embodiment of sleeve 244. Sleeve 244 may be amulti-channel sleeve. Sleeve 244 may include wall 246, channels 248,passage 250, movable members 252, and flange 254. Channels 248 mayextend from a distal end of sleeve 244 through a portion of wall 246.Channels 248 may allow instruments to be positioned and used to form aplane through soft tissue to one or more adjacent vertebrae. Anelongated member may be inserted in the tissue plane and positioned incollars of bone fastener assemblies anchored in vertebrae and coupled tosleeves. Passage 250 may allow instruments to be positioned and used tomanipulate a bone fastener assembly that is coupled to a distal end ofsleeve 244. Movable members 252 may be part of a system that couples abone fastener assembly to sleeve 244. In some embodiments, movablemembers 252 may include tool engaging portion 256. A driver may bepositioned in tool portion 256. The driver (e.g., a hex wrench) may beused to extend or retract a distal end of movable member 252. A distalend of sleeve 244 may include flange 254 that mates with a complementaryflange on a collar of a bone fastener assembly. A distal end of sleeve244 may be tapered to reduce bulk (e.g., reduce spin diameter) at asurgical site.

FIG. 27 depicts a top view of an embodiment of sleeve 244 coupled to abone fastener assembly. Tool portion 126 of bone fastener 108 is ahexalobular connection.

FIG. 28 depicts a cross-sectional representation of a portion of sleeve244 with bone fastener assembly 102 taken substantially along line 28-28of FIG. 27. Flange 254 of sleeve 244 may mate with flange 154 of collar112 to inhibit translation of the sleeve relative to the collar. Sleeve244 may also include stop 258. Stop 258 may engage a portion of collar112 to inhibit separation of walls 246. During use, stop 258 may inhibitundesired separation of bone fastener assembly 102 from sleeve 244.

FIG. 29 depicts a cross-sectional representation of a portion of sleeve244 with bone fastener assembly 102 and elongated member 104 takensubstantially along line 29-29 of FIG. 27. Distal ends of movablemembers 252 may extend into notches (e.g., notches 156 depicted in FIG.5) in collar 112. Portions of walls 246 of sleeve 244 may includethreading. Portions of movable members 252 may include threadingcomplementary to threaded portions of walls 246. Threading of movablemembers 252 may engage threading in walls 246 such that rotation of themovable members advances or retracts the movable members relative to thewalls.

As shown in FIG. 29, collar 112 may be designed such that elongatedmember 104 lies below a distal end of sleeve 244. Coupling sleeve 244 tocollar 112 above elongated member 104 may reduce bulk at a surgicalsite. With elongated member 104 coupled to collar 112 below a distal endof sleeve 244, the sleeve may be removed without interference from theelongated member of a spinal stabilization system.

FIG. 30 depicts an embodiment of sleeve 244. Sleeve 244 may be asingle-channel sleeve for use in single-level or multi-level spinalstabilization procedures. Sleeve 244 may be used at the outermostvertebrae to be stabilized during installation of a multi-levelvertebral stabilization system. Sleeve 244 may be coupled to a collar ofa bone fastener assembly with movable members 252 and/or flange 254.Instruments may be inserted through passage 250 of sleeve 244 to accessan anchored bone fastener assembly coupled to the sleeve. An instrumentmay be moved through channel 248 toward an adjacent vertebra to form atissue plane in soft tissue between sleeve 244 and the adjacentvertebra.

A sleeve may be coupled to a bone fastener assembly in various ways toinhibit movement of the sleeve relative to a collar of the bone fastenerassembly. A system used to couple the sleeve to the bone fastenerassembly may inhibit rotation and translation of the sleeve relative tothe collar.

FIG. 31 depicts a perspective view of a sleeve embodiment duringconnection of the sleeve to collar 112 of a bone fastener assembly.Sleeve 244 may include movable members 252. Movable members 252 mayinclude threaded distal end portions. FIG. 31A depicts a detailed viewof a portion of sleeve 244 and collar 112. Collar 112 may includeopenings 260. Openings 260 may be threaded. Openings 260 of collar 112may be aligned with movable members 252. A drive end of driver 262 maybe positioned in tool engaging portion 256 of movable member 252. Driver262 may be rotated to couple a threaded end of movable member 252 withthreads in opening 260. The driver may be positioned in a tool openingof second movable member 252. The driver may be used to couple athreaded end of second movable member 252 with threads in second opening260. Threaded connections between movable members 252 and collar 112 mayinhibit movement of the collar relative to sleeve 244.

A detachable member may be coupled to a collar of a bone fastenerassembly in various ways. When a detachable member is coupled to acollar, rotation and translation of the detachable member relative tothe collar may be inhibited. A system used to couple a detachable memberand collar should be simple, inexpensive to implement, and should notsignificantly weaken the mechanical strength of the collar and/or thedetachable member. Detachable members may be coupled to collars usingvarious coupling systems including, but not limited to, flanges,threaded connections, interlocking connections (e.g., ratchetingconnection systems), and/or interference fits.

In an embodiment of an interlocking connection system, a detachablemember may include an opposing pair of deflectable arms. Eachdeflectable arm may include a tooth. The deflectable arms may be forcedoutwards during coupling of a collar to the detachable member. When thecollar is coupled to the detachable member, the deflectable arms may bepositioned in channels in the collar, with the teeth positioned inindentions in the collar. The presence of the deflectable arms in thechannels of the collar may inhibit rotation and translation of thedetachable member relative to the collar. Separation of the detachablemember from the collar may be achieved by insertion of an expander inthe detachable member. The expander may be used to force the deflectablearms outwards and expel the teeth from the indentions.

FIGS. 32-45 depict embodiments of sleeves coupled to bone fastenerassemblies. In each bone fastener assembly/sleeve embodiment depicted inFIGS. 32-43 and FIG. 45, an elongated member seated in the collar of thebone fastener assembly would lie below a distal end of sleeve 244.Having the elongated member below the distal end of sleeve 244 reducesbulk at the surgical site. With sleeve 244 positioned above theelongated member, interference of the secured elongated member with thesleeve is avoided during removal of the sleeve.

FIG. 32 depicts a cross-sectional representation of sleeve 244 includingsleeve flange 254. Sleeve 244 may be rotated onto collar 112 until slot150 aligns with channel 248. Sleeve flange 254 may engage flange 154 ofcollar 112 to inhibit translation of sleeve 244 relative to collar 112of bone fastener assembly 102.

In some detachable member and collar coupling embodiments, thedetachable member and the collar may include members that work togetherto inhibit radial expansion of walls of the detachable member. FIG. 33depicts an embodiment of sleeve 244 coupled to an embodiment of bonefastener assembly 102. Sleeve 244 may include sleeve flange 254 and stop258. Sleeve flange 254 may engage flange 154 of collar 112 to inhibittranslation of sleeve 244 relative to the collar. Stop 258 may contactledge 264 of collar 112. Contact of stop 258 against ledge 264 mayinhibit release of collar 112 from sleeve 244 caused by radial expansionof walls of the sleeve. A stop in a sleeve and a ledge in a collar maybe needed in a multi-channel sleeve embodiment. A stop in a sleeveand/or a ledge in a collar may not be needed in a single-channel sleeveembodiment or in a collar for a single-level stabilization.

In some detachable member and collar coupling embodiments, a detachablemember may include a protrusion that mates with a complementary groovein a collar. Alternatively, a detachable member may include a groovethat mates with a complementary protrusion of a collar. FIG. 34 depictsa cross-sectional view of sleeve 244 with ridge 266. Ridge 266 maycouple with groove 268 in collar 112. Ridge 266 and groove 268 may forma dovetail joint. The dovetail joint may inhibit radial expansion ofsleeve walls 246. In some embodiments, such as the embodiment depictedin FIG. 35, ridge 266 and groove 268 may not form a dovetail joint.

In some embodiments, a detachable member and/or a collar may include alocking system to inhibit rotation of the detachable member relative tothe collar. The locking system may be, but is not limited to, threading,interference fits, frictional engagement, or a press-fit connection. Insome embodiments, a locking system may inhibit translation and/orrotation of a detachable member relative to a collar.

FIG. 36 depicts a top view representation of an embodiment of collar 112of a bone fastener assembly. Collar 112 includes openings 260. In someembodiments, openings 260 may be threaded. In some embodiments, openings260 may not include threading. The body of collar 112 adjacent toopenings 260 may include extra material to provide strength to thecollar.

FIG. 37 depicts a partial cross-sectional representation of anembodiment of sleeve 244 coupled to an embodiment of collar 112, such asthe collar depicted in FIG. 36. Distal end portions of movable members252 may extend into openings 260. When distal end portions of movablemembers 252 are positioned in openings 260, rotational movement ofsleeve 244 relative to collar 112 may be inhibited. Sleeve 244 mayinclude flange 254. Flange 254 may engage flange 154 of collar 112 toinhibit translation of sleeve 244 relative to the collar. In anembodiment in which distal end portions of movable members in a sleeveare threaded and openings in the collar are threaded, rotation andtranslation of the collar relative to the sleeve may be inhibited whendistal end portions of the movable members are positioned in theopenings.

As depicted in FIG. 37, portion 270 of movable member 252 may includethreading. Threading of portion 270 may engage threading in wall 246 ofsleeve 244. Engagement of threading of portion 270 with threading inwall 246 may allow distal end portion of movable member 252 to advancetowards, or retract from, a distal end of sleeve 244 when the movablemember is rotated.

FIG. 38 depicts a top view representation of an embodiment of collar 112of a bone fastener assembly. Collar 112 may include notches 156 FIG. 39depicts a partial cross-sectional representation of an embodiment ofsleeve 244 coupled to an embodiment of collar 112, such as the collardepicted in FIG. 38. Distal end portions of movable members 252 ofsleeve 244 may be extended and positioned in notches 156 of collar 112.An interference fit between the distal end portions of movable members252 and the body of collar 112 that defines the notches may inhibitrotation of sleeve 244 relative to the collar.

Portion 270 of movable member 252 may include threading. Threading ofportion 270 may engage threading in wall 246 of sleeve 244. Engagementof threading of portion 270 with threading in wall 246 may allow adistal end portion of movable member 252 to advance towards, or retractfrom, a distal end of sleeve 244 when the movable member is rotated.

In an embodiment, an inner sleeve may be positioned in a sleeve toinhibit translation and/or rotation of the sleeve relative to a collarof a bone fastener assembly. FIG. 40 depicts a cross-sectional view ofsleeve 244 with inner sleeve 272. A distal end of inner sleeve 272 maycontact an upper end of collar 112. A proximal portion of inner sleeve272 may engage a proximal portion of sleeve 244. The engagement mayallow inner sleeve 272 to apply a force against collar 112 that pressesflange 154 against flange 254 of sleeve 244 to inhibit translation ofthe sleeve relative to the collar. The engagement may be, but is notlimited to, a threaded connection, an interference fit, a frictionalfit, or a keyway type of connection.

In some embodiments, a distal end of an inner sleeve may be roughened ortextured to frictionally engage a proximal surface of the collar. Thefrictional engagement may inhibit rotation of the sleeve relative to thecollar. In some embodiments, inner sleeve 272 may include passage 274. Apin may pass through passage 274 into an opening in collar 112. When apin is positioned through passage 274 into the opening, rotation ofsleeve 244 relative to collar 112 may be inhibited.

In some embodiments, threading may be used to couple a detachable memberto a collar. FIG. 41 and FIG. 42 depict partial cross-sectionalrepresentations of sleeves 244 that couple to collars 112 by threadedconnections. Sleeves 244 may include female threading that iscomplementary to male threading of collar 112. In some embodiments,threading of the sleeve and threading of the collar may be modifiedthreads.

FIG. 43 depicts a partial cross-sectional representation of sleeve 244that couples to collar 112 by a threaded connection. Sleeve 244 mayinclude male threading, and collar 112 may include complementary femalethreading. In some embodiments, portion 276 of collar 112 that includesthreading which mates with threading of sleeve 244 may be a break-offsection. Collar 112 may be held in a fixed position. Torque may beapplied to sleeve 244 to shear off portion 276.

In some embodiments, a detachable member may include a pair of hingedarms configured to couple to a collar. FIG. 44 and FIG. 45 depictembodiments of sleeves that include hinged portions. Sleeve 244 mayinclude arms 278. Arms 278 may be pivotally coupled together by hinge280. Hinge 280 may be located near a proximal end of sleeve 244. In somesleeve embodiments, sleeve 244 may include a locking element or abiasing element (e.g., a spring) near or at hinge 280. A locking elementor biasing element may cause a clamping force to be exerted on collar112 to maintain the collar in the sleeve and/or to inhibit rotation ofcollar 112 in sleeve 244. In some embodiments, such as in the embodimentdepicted in FIG. 44, flange 254 of sleeve 244 may contact a bottomportion of collar 112. In some embodiments, such as in the embodimentdepicted in FIG. 45, flange 254 of sleeve 244 may contact flange 154 ofcollar 112.

In some detachable member embodiments, proximal portions of detachablemembers may be chamfered to allow ends of the detachable members to moreclosely approach each other than detachable members with a uniform crosssection. FIG. 46 depicts sleeves 244 coupled to collars 112 engaged inadjacent pedicles 164. Sleeves 244 may include chamfered surfaces 282.Chamfered surfaces 282 may reduce space between proximal ends of sleeves244. During some surgical procedures, only one of the sleeves may bechamfered. During some surgical procedures, the use of a sleeve with achamfered surface may allow for a smaller incision than required whenusing non-chamfered sleeves. In some embodiments, other types ofdetachable members may be used to reduce space between proximal ends ofdetachable members. Other types of detachable members may include, butare not limited to, detachable members of different lengths, detachablemembers of different diameters, and detachable members with flexible endportions.

Detachable members may be of various lengths. Detachable members ofdifferent lengths may be used in the same surgical procedure. Adetachable member length used in a spinal stabilization procedure may bedetermined by a patient's anatomy. Detachable members may be just shortenough to allow manipulation by a medical practitioner above an incisionin a patient. In some embodiments, detachable members may be about 3.5to about 11.5 cm long. For example, a single-channel detachable membermay be about 10 cm long. In some embodiments, detachable members may beabout 11.5 cm to about 14 cm long. For example, a single-channel or amulti-channel detachable member may be about 12.5 cm long. Amulti-channel detachable member may be longer than a single-channeldetachable member. In some embodiments, a multi-channel detachablemember may be at least about 15 cm long. For example, a multi-channeldetachable member may be about 16 cm long. Detachable members that aretoo long may require a longer incision and/or a larger tissue plane forinsertion of a spinal stabilization system. Insertion of an elongatedmember may be more difficult with detachable members that are longerthan necessary. Detachable members with excess length may be bulky andhard to manipulate during a surgical procedure.

A detachable member may be flexible over its entire length or include aflexible portion near a proximal end of the detachable member. Aflexible portion may allow positioning of a proximal portion of adetachable member in a desired location. A flexible portion may beproduced from any of various materials including, but not limited to, asurgical grade plastic, rubber, or metal. A flexible portion may beformed of various elements, including, but not limited to, a tube, achannel, or a plurality of linked segments.

FIG. 47 depicts an embodiment of sleeve 244 with a connection thatallows movement of first portion 284 relative to second portion 286.First portion 284 may be coupled to collar 112 of a bone fastenerassembly. Second portion 286 may connect to first portion 284 at linkage288. Linkage 288 may include, but is not limited to, a locking element,a pivot point, a hinge, or a pin. In some embodiments, the linkage maybe a ball and socket type of connection that allows rotational motion ofsecond portion 286 relative to first portion 284. During some spinalstabilization procedures, a detachable member without a second portionthat is able to move relative to a first portion may be used at onevertebra, and a detachable member with a second portion that is able tomove relative to a first portion may be used at one or more vertebraethat are to be stabilized.

When bone fasteners of polyaxial bone fastener assemblies are positionedin vertebral bone, detachable members coupled to collars of the bonefastener assemblies may be moved in desired positions. During surgery, adetachable member in a patient may be oriented towards an adjacentvertebra that is to be stabilized to reduce the required incision size.In some embodiments, channels of the detachable members may be alignedso that an elongated member may be positioned in collars of the bonefastener assemblies. FIG. 48 depicts an orientation of three sleeves.Sleeves 244, 244′ may couple to collars 112, 112′. Bone fasteners 108,108′ may be inserted into vertebrae. Single-channel sleeves 244 may becoupled to collars 112 before insertion of bone fasteners 108 into twoouter pedicles to be stabilized. Multi-channel sleeve 244′ may becoupled to collar 112′ before insertion of bone fastener 108′ into acentral pedicle of the three adjacent pedicles. Single-channel sleeves244 may be angled towards multi-channel sleeve 244′. In certainembodiments, multi-channel detachable members may be coupled to allthree pedicles. In other embodiments, differently shaped detachablemembers (e.g., circular, oval) may be used in one or more of thepedicles. Channels of the detachable members may be aligned so that anelongated member may be moved down the detachable members and intocollars of the bone fastener assemblies

In some embodiments, channels of detachable members may face a directionother than toward each other. FIG. 49 depicts sleeves 244 coupled tocollars 112 oriented at an angle so that channels 248 of sleeves 244face in different directions. An elongated member may be curved in anappropriate shape to engage slots 150 in collars 112 when channels 248of sleeves 244 are angled. In some embodiments, channels in thedetachable member may not be longitudinal channels down the length ofthe detachable member. In embodiments of detachable members withnon-longitudinal channels, the channels of two adjacent detachablemembers may not face towards each other when the openings of collarscoupled to the detachable members are aligned.

In an embodiment, a frame may couple to two or more detachable members.FIG. 50 depicts a perspective view of sleeves 244 coupled to frame 290.As used herein, a “frame” includes any of a variety of structuralelements including, but not limited, rods, bars, cages, or machinedblocks. In some embodiments, frame 290 may provide a rigid couplingbetween sleeves 244. In other embodiments, frame 290 may allow forangular or translational movement between sleeves. For example, frame290 may include slidable elements that allow sleeves to be translatedtoward each other or away from each other to facilitate compression ordistraction of vertebrae. Alternatively, frame 290 may enable sleeves244 to pivot toward each other or away from each other. In someembodiments, frame 290 may allow for movement of sleeves 244 tofacilitate spinal reduction.

After a bone fastener assembly is coupled to a detachable member, adriver may be coupled to a bone fastener of the bone fastener assembly.The driver may be used to insert the bone fastener into vertebral bone.

FIG. 51 depicts an embodiment of driver 292 positioned in sleeve 244.Sleeve 244 is coupled to bone fastener assembly 102. Driver 292 may becoupled to collar 112 and to bone fastener 108 of bone fastener assembly102. Coupling driver 292 to collar 112 and to bone fastener 108 mayensure proper alignment of the driver relative to the bone fastener.Coupling driver 292 to collar 112 and to bone fastener 108 may alsoinhibit movement of the collar relative to the bone fastener duringinsertion of the bone fastener.

Driver 292 may include outer shaft 294, inner shaft 296, and removablehandle 236. Outer shaft 294 may include threading 298 and texturedportion 300. A portion of outer shaft 294 may be positioned in a passagethrough sleeve 244 (passage 250 shown in FIG. 30). Threading 298 maycouple to a modified thread of collar 112. Textured portion 300 mayfacilitate rotation of outer shaft 294 so that threading 298 engages themodified thread of collar 112. When threading 298 engages the modifiedthread of collar 112, driver 292 may be securely coupled to bonefastener assembly 102, which is securely fastened to sleeve 244.

A distal end of inner shaft 296 may be coupled to bone fastener 108during use. Inner shaft 296 may be coupled at a proximal end toremovable handle 236 during use. Inner shaft 296 may be rotatablerelative to outer shaft 294 so that bone fastener 108 can be insertedinto vertebral bone. A proximal portion of inner shaft 296 may includeat least one flat portion that fits in a mating portion of removablehandle 236. Removable handle 236 may be the same removable handle thatis used with a bone tap that forms a threaded opening in vertebral bonefor a bone fastener Removable handle 236 may be removed from driver 292during insertion of a guide wire through the driver so that the guidewire may be held in at least one place at all times. In someembodiments, a removable handle for the driver may be unnecessary giventhe length of the guide wire and/or the length of the driver (e.g., along guide wire and/or a short driver).

FIG. 52 depicts a cross-sectional representation of a portion of anembodiment of a driver that is coupled to bone fastener 108 and collar112 of a bone fastener assembly. Collar 112 is coupled to sleeve 244.Sleeve 244 is positioned in dilator 302. In some embodiments, clearancebetween outer shaft 294 and sleeve 244 may be relatively small. In someembodiments, the clearance between outer shaft 294 and sleeve 244 mayrange from about 0.1 mm to about 0.75 mm. For example, the clearancebetween outer shaft 294 and sleeve 244 may be about 0.25 mm (i.e., aninner diameter of the sleeve may be about 0.5 mm greater than an outerdiameter of the outer shaft). Also, clearance between sleeve 244 anddilator 302 may be relatively small. The small clearances may inhibitundesired movement of the instruments relative to each other and/orreduce bulkiness at the surgical site.

Thread 298 of outer shaft 294 of the driver may couple to modifiedthread 148 of collar 112. Head 304 of inner shaft 296 of the driver maycouple to tool portion 126 of bone fastener 108. Head 304 may have acomplementary shape to tool portion 126 of bone fastener 108. A guidewire may be inserted into a distal end of passage 114 of bone fastener108 and through passage 306 of the driver. When the guide wire isinserted into passage 114 and passage 306, a removable handle may not becoupled to inner shaft 296.

During a minimally invasive surgical procedure, a plane may be createdin tissue from a first vertebra to a second vertebra. An elongatedmember may be positioned in the plane during the surgical procedure. Insome embodiments, a tissue plane may be formed using a targeting needle.The targeting needle may be positioned at the first vertebra. The distalend of the needle may be moved toward the second vertebra to form theplane while maintaining a position of the needle at a surface of theskin. The needle may be moved back and forth a number of times toclearly establish the plane. Care may need to be taken to avoid bendingthe targeting needle during establishment of the plane.

In some embodiments, a tissue wedge may be used to form a plane intissue between a first vertebra and a second vertebra. FIG. 53 depictsan embodiment of tissue wedge 308. Tissue wedge 308 may include handle310 and blade 312. Handle 310 may allow blade 312 to be easilypositioned at a desired location.

Blade 312 may be a double-wedged blade. Blade 312 may have adiamond-like shape. Edges of blade 312 may be blunt to avoid severingtissue during use of tissue wedge 308. Distal end 314 of blade 312 maybe rounded. A shape of distal end 314 may inhibit damage to tissue andmay facilitate movement of blade 312 towards a target location duringformation of a plane in tissue between vertebrae. In some tissue wedgeembodiments, tissue wedge 308 may include hook 316. Cutting edge 318 inhook 316 may be used to sever portions of tissue (e.g., fascia) throughwhich blade 312 cannot form a plane. Cutting edge 318 may be oriented inblade 312 so that severing of tissue results when tissue wedge 308 ispulled away from the spine.

An estimating tool may be used to estimate a distance between bonefastener assemblies anchored in vertebrae. The bone fastener assembliesmay be part of a single-level or multi-level spinal stabilizationsystem. The distance estimated by an estimating tool may be used todetermine a desired length of an elongated member to be positioned incollars of the anchored bone fastener assemblies. FIG. 54 depicts anembodiment of estimating tool 320 with handle 322 and shaft 324. Arms326 may be pivotably coupled to coupling portion 325 of shaft 324.Distal ends of arms 326 may be rounded. In some embodiments, distal endsof arms 326 may include members 330. Members 330 may be rounded (e.g.,spherical) or elongated (e.g., tubular). Members 330 may also have othershapes to meet specific needs or requirements. In embodiments, a shapeand/or a size of members 330 may be designed to fit snugly intodetachable members coupled to a spinal stabilization system.

Activator 328 may be located at a proximal end of handle 322. Withactivator 328 unengaged, a biasing element (e.g., a spring, springs,and/or elastic member) in coupling portion 325 may allow arms 326 toassume a fully extended position. With arms 326 in a fully extendedposition, members 330 may achieve a maximum separation distance.Estimating tool 320 may be designed such that a maximum separationdistance of members 330 exceeds an expected distance between anchoredbone fastener assemblies. Fully extended arms 326 may be manuallycompressed and inserted into passages of sleeves coupled to anchoredbone fastener assemblies. For a multi-level system, arms 326 may beinserted in detachable members coupled to the outermost bone fastenerassemblies while one or more detachable members coupled to one or moreinner vertebrae are held out of the way. With activator 328 unengaged,the biasing element in coupling portion 325 may force members 330against inner walls of the detachable members.

Estimating tool 320 may be advanced toward the anchored bone fastenerassemblies. In some embodiments, estimating tool 320 may be advancedtoward the anchored bone fastener assemblies until members 330 contactcollars and/or bone fasteners of the bone fastener assemblies. Withmembers 330 contacting collars and/or bone fasteners, activator 328 ofestimating tool 320 may be engaged. Engaging activator 328 of estimatingtool 320 may limit the biasing element such that the distance betweenouter surfaces of members 330 does not exceed the distance between theanchored bone fastener assemblies. With activator 328 engaged and thedistance between outer surfaces of members 330 fixed to indicate thedistance between the anchored bone fastener assemblies, estimating tool320 may be moved upwards to remove the estimating tool from the patient.When estimating tool 320 is moved upwards, arms 326 may compress tofacilitate removal of the estimating tool from the detachable members.

Once removed from the detachable members, the biasing element mayrestore the distance between outer surfaces of members 330 to indicatethe separation between anchored bone fastener assemblies. The distancebetween members 330 (e.g., the distance between outer surfaces of themembers) may be used to estimate a length of an elongated member neededto couple the anchored bone fastener assemblies. The distance betweenmembers 330 may be read using a scale provided in the instrumentationkit. In some embodiments, the scale may be indicia or etching on asurface of the instrumentation kit. In an embodiment, a length of anelongated member may be chosen to be greater than a distance betweenmembers 330 to allow for bending of the elongated member and/or to allowthe elongated member to extend beyond the collars of the anchored bonefastener assemblies. For example, 15 mm may be added to the distancebetween members 330. In some embodiments, a length of an elongatedmember may be chosen such that the elongated member extends 2 mm or morebeyond the collars. In certain embodiments, a length of an elongatedmember may be chosen such that ends of the elongated member do notextend from the collars.

In the embodiment shown in FIG. 55, arms 326 of engaging tool 320 may besubstantially parallel to each other and/or touching each other withactivator 328 unengaged. Engaging activator 328 may cause separation ofarms 326 at an angle, such that a distance between distal ends of thearms is greater than a distance between proximal portions of the arms.Estimating tool 320 may be inserted (ergo, with arms 326 together) indetachable members coupled to bone fastener assemblies anchored invertebral bone. Activator 328 may be engaged and activated until arms326 extend through channels of the detachable members and contact innersurfaces of the detachable members. Arms 326 may contact bone fastenersin the bone fastener assemblies. With arms 326 extended to meetresistance in the detachable members, estimating tool 320 may bewithdrawn from the detachable members. During withdrawal of estimatingtool 320 from the detachable members, arms 326 may be compressed towardeach other as the estimating tool is moved up the detachable members andout of the body. After withdrawal of estimating tool 320 from thedetachable members, arms 326 may extend back to the separation achievedwhen the arms were touching the bone fasteners. The distance betweenextended arms 326 may be used to estimate a length of an elongatedmember needed to couple the anchored bone fastener assemblies.

In some embodiments, an estimating tool may include a gage. FIG. 56depicts an embodiment of estimating tool 320 with gage 332. With arms326 of estimating tool 320 positioned together, gage 332 may have or maybe set to a zero reading. With arms 326 extended to meet resistance insleeves 244, gage 332 may provide an estimate of the distance betweenthe sleeves. The distance between the sleeves may be used to estimate alength of an elongated member needed to couple the anchored bonefastener assemblies. In an embodiment, a length of an elongated membermay be chosen to be greater than the distance measured by a gage toallow the elongated member to extend beyond slots of collars of anchoredbone fastener assemblies.

In some embodiments, an elongated member positioner may be used to guidean elongated member through detachable members and to position theelongated member in collars proximate pedicles of vertebrae. FIG. 57depicts an embodiment of elongated member positioner 334. Elongatedmember positioner 334 may include outer shaft 336, handle 338, innershaft 340, and grasping member 342. In some embodiments, grasping member342 may be a hook. A first end (i.e., proximal end) of outer shaft 336may be connected to handle 338. A second end (i.e., distal end) of outershaft 336 may be coupled to grasping member 342. Inner shaft 340 maypass through handle 338 and outer shaft 336. A second end (i.e., distalend 344) of inner shaft 340 may contact an elongated member positionedin grasping member 342. A first end proximal end 346) of inner shaft 340may extend from handle 338. Proximal end 346 of inner shaft 340 may be aknob or a thumb plate. An amount of force applied to an elongated memberpositioned between grasping member 342 and distal end 344 of inner shaft340 may be controlled by the amount of pressure applied to proximal end346 of inner shaft 340. Pressure may be applied to proximal end 346 ofinner shaft 340 manually or mechanically. Mechanical means of applyingpressure to proximal end 346 of inner shaft 340 include, but are notlimited to, forceps handles and an adjustable rotor.

Distal end 344 of inner shaft 340 may be positioned proximate graspingmember 342. An elongated member may be positioned between graspingmember 342 and distal end 344 of inner shaft 340 of positioning tool 334before or after initial insertion of the elongated member into a sleeve.The elongated member may be held between grasping member 342 and distalend 344 of inner shaft 340 with pressure applied to proximal end 346 ofthe inner shaft. Distal end 344 of inner shaft 340 may be contoured(e.g., curved) to allow some motion (e.g., rocking motion) of theelongated member while the elongated member is coaxed into position withpositioning tool 334. During some installation procedures, positioningtool 334 may remain coupled to an elongated member until the elongatedmember is secured in collars of anchored bone fastener assemblies withclosure members.

In some cases, pressure supplied to an elongated member with anelongated member positioner may not be sufficient to seat the elongatedmember in a collar. A seater may be used in conjunction with anelongated member positioner to maneuver an elongated member into one ormore collars. During some procedures, an elongated member positioner maybe removed from the elongated member before using the seater. Duringsome procedures, the elongated member positioner may remain attached tothe elongated member until closure members are secured to bone fastenerassemblies to form a spinal stabilization system.

Seater 348, shown in FIG. 58, may include handle 350 and groove orgrooves 352. A portion of an elongated member to be positioned incollars may fit in grooves 352. In an embodiment, an elongated memberpositioner may be used to align an elongated member proximate slots inone or more collars coupled to pedicles of vertebrae. Groove 352 ofseater 348 may be positioned at a desired position along a length of theelongated member. A user may apply downward force with handle 350 toseat the elongated member in a collar as the elongated member positioneris used to guide the elongated member into position.

After an elongated member has been positioned and seated in collars asdesired, closure members may be used to secure the elongated member tothe collars. FIGS. 59A and 59B depict perspective views of driver 354.Driver 354 may be used to position a closure member in a collar of abone fastener assembly. As shown in FIG. 59A, driver 354 may includehandle 356, elongated portion 358, and coupling portion 360. Couplingportion 360 may be used to engage closure member 106. Coupling portion360 may engage tool portion 170 of closure member 106, shown in FIG.59B. In some embodiments, driver 354 may include an inner shaft. Theinner shaft may couple the closure member to driver 354. The inner shaftmay couple to the tool portion of the closure member so that the toolportion is securely held after the tool portion is sheared from theclosure member. In some embodiments, an end of inner shaft may be pressfit into the tool portion. In some embodiments, the inner shaft mayinclude a threaded end portion that engages a mating thread in the toolportion. Rotation of the inner shaft may allow closure member 106 to belocked in coupling portion 360 of driver 354. Knob 362 may be used torotate the inner shaft.

FIG. 60A depicts driver 354 with coupled closure member 106 positionedfor insertion in sleeve 244. After insertion of driver 354 in sleeve244, closure member 106 may be positioned proximate collar 112. Withdriver 354 positioned in sleeve 244, as shown in FIG. 60B, the drivermay be rotated to advance closure member 106 in collar 112 and secureelongated member 104 to the collar. When closure member 106 is snug andelongated member 104 is secured, driver 354 may be disengaged from theclosure member and removed from sleeve 244. In an embodiment, driver 354may be used to shear off the tool portion of secured closure member 106.In some embodiments, the coupling portion of the driver may capture thesheared tool portion of the closure member. In certain embodiments,driver 354 may include a mechanism to dislodge a closure member and/or atool portion of a closure member from the distal end of the driver.

In some embodiments, a detachable member may be held with a countertorque wrench as the tool portion of a closure member is sheared off. Inan embodiment, about 90 in-lbs of torque may be required to shear offthe tool portion of a closure member. A counter torque wrench mayinhibit transfer of force to the patient when a closure member is beingsecured to a collar. FIG. 61 depicts an embodiment of counter torquewrench 364 used to inhibit application of torque to a patient's spineduring shearing of a tool portion of a secured closure member. Sleeve244 may fit in opening 366 of counter torque wrench 364. Counter torquewrench 364 may be positioned near a proximal end of sleeve 244 duringuse. Force may be applied to counter torque wrench 364 in a directionopposite to rotational force applied to driver 354 to shear off the toolportion of a secured closure member. Opening 366 in torque wrench 364may be of any shape to accommodate a cross-sectional shape of sleeve 244and inhibit rotation of the sleeve during use.

FIG. 62 depicts an embodiment of counter torque wrench 368 designed toaccommodate sleeves. Counter torque wrench 368 may include hollow shaft370 and handle 372. Groove 374 may be located at a distal end of hollowshaft 370. FIG. 63 depicts counter torque wrench 368 fitted overmulti-channel sleeve 244A. In an embodiment, hollow shaft 370 may beinserted through an opening in the body over sleeve 244 and advancedtoward the spine until elongated member 104 is seated in groove 374.Counter torque wrench 368 may engage the spinal stabilization system.Force may be applied to counter torque wrench 368 in a directionopposite to rotational force applied to a driver used to shear off atool portion of a secured closure member. During a minimally invasivespinal stabilization procedure, counter torque wrench 368 may be usedwith various types of detachable members, including single-channelsleeves and multi-channel sleeves.

Minimally invasive procedures may involve locating a surgical site and aposition for a single skin incision to access the surgical site. Theincision may be located above and between (e.g., centrally between)vertebrae to be stabilized. An opening under the skin may be enlarged toexceed the size of the skin incision. Movement and/or stretching of theincision, bending of an elongated member, and angulation of collars ofbone fastener assemblies may allow the length of the incision and/or thearea of a tissue plane to be minimized. In some embodiments, minimallyinvasive insertion of a spinal stabilization system may not bevisualized. In certain embodiments, insertion of a spinal stabilizationsystem may be a top-loading, mini-opening, muscle-splitting, screwfixation technique.

Insertion of a spinal stabilization system may include graduallyincreasing the diameter of an opening formed in a pedicle and/orvertebral body to accept a bone fastener assembly. For example, atargeting needle may have outer diameter of about D. A bone awl insertedafter the targeting needle may have an outer diameter incrementallylarger than the outer diameter of the targeting needle. As used herein,an incrementally larger diameter may be large enough to allow a snug butadjustable fit. For example, the bone awl may have outer diameter ofabout (D+x). A tap portion of a bone tap inserted after the bone awl mayhave a minor diameter of about (D+2x). A bone fastener may have a minordiameter of about (D+3x). In some embodiments, x may be between about0.1 mm and about 1.0 mm. For example, x may be about 0.5 mm. Incrementalsizing of the targeting needle, bone awl, tap, and bone fastener maypromote a proper fit of the bone fastener in the vertebra to bestabilized.

In an embodiment of a spinal stabilization system insertion method, thepatient may be placed in a prone position on a radiolucent table withclearance available for a C-arm of a fluoroscope. For example, a Jacksontable with a radiolucent Wilson frame attachment may be used. Theability to obtain high quality images is very important. Bolsters,frames, and pads may be inspected for radiolucency prior to theoperation. Placing the patient in a knee-chest position (e.g., using anAndrews table) should be avoided. Care should be taken to avoid placingthe patient's spine in kyphosis during positioning of the patient.

The C-arm of the fluoroscope should be able to freely rotate between theanteroposterior, lateral, and oblique positions for optimalvisualization of pedicle anatomy during the procedure. The arm should berotated through a full range of motion prior to beginning the procedureto ensure that there is no obstruction or radio-opaque object in theway. The fluoroscope may be positioned so that Ferguson views and“bullseye” views are obtainable. Once the patient is positioned and theability to obtain fluoroscopic images of the target levels forinstrumentation has been confirmed, the patient may be prepared anddraped sterilely.

For most of the lumbar region, the vertebral pedicle is an obliquelyoriented cylindrical corridor. The angulation varies by approximately 5degrees per level (e.g., L1: 5 degrees; L5: 25 degrees). A pre-operativefine-cut computed tomography image may be examined to determine anyunique anatomy of the patient. Acquiring the pedicle in the most lateraland superior quadrant of the pedicle may be desirable to avoid theoverriding facet during a minimally invasive procedure. A lateral entrypoint may allow for better screw convergence as well as lessinterference with the superior adjacent level facet joint. A targetingneedle may be passed in a medial and inferior trajectory, thus followingthe natural pathway of the pedicle. Frequent fluoroscopic inspection inboth an anteroposterior and lateral plane may ensure proper passage ofthe needle as the needle is inserted into vertebral bone.

Various techniques may be used to plan the skin incisions and entrypoints. In one embodiment, the planning sequence for a single-levelstabilization may include the following four steps. First, ananteroposterior image may be obtained with the spinous processescentered at the target vertebral bodies. Vertical lines passing throughmidpoints of pedicles that are to receive bone fasteners may be markedon the patient. The lines do not represent skin entry points. The linesare markers of pedicle entry points used to estimate angles at whichtargeting needles to be inserted to contact the pedicles. In someembodiments, sets of vertical lines may be drawn corresponding to thelateral edges of the pedicles instead of lines corresponding to themidpoints of the pedicles.

Second, horizontal lines may be marked approximately through the centersof the pedicles (mid-pedicle lines) on the patient. In some embodiments,the lines may be drawn on the superior side of the center axes (superiorto the mid-pedicle).

Third, an oblique or “bullseye” view (idea, down a longitudinal axis ofa pedicle) may be obtained on each side of the patient for each pediclethat is to be stabilized. Vertical oblique view lines may be marked onthe skin at the midpoints of each of the pedicles that are to receive abone fastener. The oblique view lines may be drawn in a different colorthan the vertical lines drawn during the first step. In someembodiments, vertical lines may be drawn corresponding to the lateraledges of the pedicles instead of lines corresponding to the midpoints ofthe pedicles.

The oblique view lines may be about 2 cm to about 3 cm away from thelateral pedicle border lines marked in the first step. For largerpatients, the oblique view line may be greater than about 3 cm away fromthe midline marked in the first step. For smaller patients, the obliqueview line may be closer than about 2 cm away from the midline marked inthe first step. The intersection of the oblique view lines with thehorizontal lines drawn in the second step may represent skin entrypoints for a targeting needle as the targeting needle passes throughsoft tissue at an angle towards the bony pedicle entry point. A sidefluoroscopic image, the horizontal lines, and the vertical lines mayhelp the surgeon triangulate between the skin entry points and bonyentry points.

Fourth, an incision may be made in the skin between mid-pedicle linesalong the vertical oblique view lines. The skin incision may be fromabout 2 cm to about 4 cm long. In some embodiments, the incision may befrom about 2.5 cm to about 3 cm long. Limiting the length of theincision may enhance patient satisfaction with the procedure. Theincisions may be pre-anesthetized with, for example, 1% lidocaine with1:200,000 epinephrine. To blunt the pain response, a long spinal needlemay be used to dock on the bone entry point and inject the plannedmuscle path in a retrograde fashion as well. Once the incision has beenmade, tissue surrounding the incision may be pulled and/or stretched toallow access to a target location in a vertebra.

After sterile preparation and draping, the pedicle entry points may befluoroscopically rechecked to ensure that the previously marked linescorrespond to the intersection of the midline of the transverse processand the lateral joint and pars interarticularis. The intersection of thefacet and the transverse process provides a starting point that may helpavoid the canal and follow the natural inclination of lumbar pedicles.For the spinal stabilization system described, in which sleeves coupledto bone fastener assemblies are substantially unconstrained by insertionangles of the bone fasteners, patient anatomy may determine the mostadvantageous insertion angles of the bone fasteners.

A scalpel may be used to make a stab wound at the junction of an obliqueview line and a mid-pedicle line. In an embodiment, the scalpel may be a#11 scalpel. A targeting needle may be passed through the incision in anoblique lateral to medial trajectory towards the bony entry pointdefined by a lateral pedicle border line. The C-arm of the fluoroscopemay be placed in an anteroposterior position for this maneuver.

As the targeting needle encounters the bony anatomy, anteroposteriorfluoroscopic images may be used to place the tip of the needle at theupper outer quadrant of the pedicle. In some embodiments, the needle maybe walked medially along the transverse process to the pedicle entrypoint. In some embodiments, the needle tip may be docked by lightlytapping the tip into the bone with a mallet or other impact device todrive the tip into the bone. In some embodiments, the needle tip may bedocked by applying downward pressure to the targeting needle to forcethe tip into the bone.

The fluoroscope may then be moved to a lateral position. The surgeon maycorrect the sagittal trajectory of the needle by moving the needle in ananterior or posterior direction to match the vector of the pediclecorridor. In some embodiments, a mallet or other impact device may beused to gently advance the targeting needle into the pedicle halfway tothe pedicle-vertebral body junction. In other embodiments, force may beapplied to the targeting needle to drive the targeting needle into thepedicle halfway to the pedicle-vertebral body junction. Ananteroposterior image may then be obtained to confirm that the needle isapproximately halfway across the pedicle in the anteroposterior view. Ifthe tip is more than halfway across the pedicle in a lateral to medialprojection, the trajectory may be too medial. Further advancement of theneedle may risk passing the needle through the spinal canal. The needlemay be repositioned. A new starting point or new trajectory may beobtained. If the anteroposterior image demonstrates that the needle issignificantly lateral in the pedicle, then the needle may have passedalong the lateral portion of the pedicle. A needle that has passed alongthe lateral portion of the pedicle may be withdrawn and repositioned.

Once a good trajectory has been obtained, the targeting needle may beadvanced using a mallet. In some embodiments, the needle may be pushedin without a mallet. The targeting needle may be advanced to thejunction of the pedicle and vertebral body under lateral fluoroscopicguidance. FIG. 64A depicts targeting needle 198 advanced to the junctionof pedicle 164. At this point, confirmation of position and trajectoryshould be repeated under anteroposterior fluoroscopy. Targeting needle198 may be further advanced to a desired depth within vertebral body 166using a mallet or applied force. FIG. 64B depicts targeting needle 198advanced to the desired depth.

A scale on targeting needle 198 may be used to approximate a length of abone fastener to be used. A first depth of targeting needle 198 may bemeasured relative to body surface 376 when pedicle 164 is firstencountered. A second depth of targeting needle 198 may be measuredrelative to body surface 376 after the targeting needle has beenadvanced to the desired depth in vertebral body 166. An approximatelength of the pedicle screw to be used may be determined by taking adifference between the depth measurements.

After targeting needle 198 has been advanced into the bone, member 202of the targeting needle (shown in FIG. 64B) may be removed from thetargeting needle. FIG. 64C depicts outer housing 200 with the memberremoved. After removal of the member, a guide wire may be placed througha passage in targeting needle 198 into vertebral body 166. FIG. 64Ddepicts targeting needle 198 with guide wire 218 positioned through thepassage in the targeting needle. Lateral fluoroscopic images may beobtained to indicate the position of guide wire 218. In someembodiments, guide wire 218 may be pushed into vertebral body 166. Incertain embodiments, guide wire 218 may be advanced about 1 cm beyond anend of outer housing 200 to secure the guide wire in vertebral body 166.In some embodiments, a small diameter tissue dilator may be placed overthe guide wire and positioned on an upper surface of the targetingneedle. The tissue dilator may provide stability to the guide wire.Added stability from the dilator may allow the guide wire to besuccessfully tapped into the vertebral body with a small mallet. Careshould be taken to avoid kinking guide wire 218. After guide wire 218 issecured in vertebral body 166, outer housing 200 may be removed from thepatient. FIG. 64E depicts guide wire 218 after removal of the targetingneedle.

Once the guide wire has been passed through the targeting needle and thetargeting needle has been removed, the guide wire may be used as a guideto position one or more successively sized dilators around a targetlocation in a pedicle. A dilator may be a conduit with a regular shape(e.g., cylindrical) or an irregular shape (e.g., C-shaped). A dilatormay form an opening through soft tissue to the pedicle For patients witha thick fascia, it may be advantageous to make a nick in the fascia witha scalpel blade to facilitate passage of the dilators. The dilators maybe passed sequentially over the guide wire. The dilators may be rotatedduring insertion to facilitate dilation of surrounding tissue. Thedilators may be inserted until the leading edges contact the pedicle. Adistal end of a dilator may be tapered to facilitate positioning of thedilator proximate the pedicle. An instrumentation set for a spinalstabilization system may include two, three, four, or more successivelysized dilators.

FIG. 65A depicts first dilator 302A positioned around guide wire 218.First dilator 302A may have an inner diameter just slightly larger thanan outer diameter of guide wire 218. As used herein, “an inner diameterjust slightly larger than an outer diameter” may mean that the innerdiameter is between about 0.03 mm and about 1.0 mm greater than theouter diameter. For example, an inner diameter of first dilator 302A maybe about 0.5 mm greater than the outer diameter of guide wire 218. FIG.65B depicts second dilator 302B positioned around first dilator 302A.Second dilator 302B may have an inner diameter just slightly larger thanan outer diameter of first dilator 302A. FIG. 65C depicts third dilator302C and fourth dilator 302D and positioned around second dilator 302B.Third dilator 302C may have an inner diameter just slightly larger thanan outer diameter of second dilator 302B. Fourth dilator 302D may havean inner diameter slightly larger than an outer diameter of thirddilator 302C. Once fourth dilator 302D is in position, dilators 302A,302B, 302C may be removed, starting with dilator 302A. Lengths ofdilators in a successively sized set may decrease with increasingdiameter to facilitate removal of the smaller dilators. Care should betaken to avoid dislodging guide wire 218 during insertion and removal ofthe dilators. FIG. 65D depicts fourth dilator 302D positioned aroundguide wire 218 following removal of dilators 302A, 302B, 302C.

After tissue dilation has been achieved, a large diameter dilator (erg,third dilator 302C or fourth dilator 302D shown in FIG. 65C) may be usedto guide a bone fastener assembly and/or insertion instruments toward atarget location in a pedicle. FIGS. 66A-66F depict portions of aprocedure for preparation of pedicle 164 and vertebral body 166 forreceiving a bone fastener assembly. FIG. 66A depicts bone awl 222positioned over guide wire 218 in dilator 302 such that a tip of thebone awl is on or near a surface of pedicle 164. Bone awl 222 may bedriven downwards into pedicle 164 to breach cortical bone of the pedicleFIG. 66B depicts a position of bone awl 222 after pedicle 164 has beenbreached. After pedicle 164 is breached, bone awl 222 may be removedfrom dilator 302. FIG. 66C depicts guide wire 218 and dilator 302 afterremoval of bone awl 222. In some embodiments, an initial passage may beformed in the pedicle and the vertebral body using a drill or a drilland tap combination.

FIG. 66D depicts tap 230 positioned in dilator 302. After pedicle 164 isbreached, tap 230 may be inserted over guide wire 218 into dilator 302.In an embodiment, dilator 302 may be third dilator 302C. Tap 230 may besized to fit snugly inside third dilator 302C. In some embodiments,dilator 302 may be fourth dilator 302D. In certain embodiments, fourthdilator 302D may be inserted over third dilator 302C after bone has beentapped through the third dilator. Tapping through third dilator 302Crather than fourth dilator 302D may introduce less bulk at the targetsite of a pedicle during the tapping procedure. In some embodiments, anouter diameter of a sleeve coupled to a bone fastener assembly to beinserted in the pedicle may be substantially the same as an outerdiameter of third dilator 302C.

Tap 230 may include removable handle 236 and indicia 240. Indicia 240may be a scale. When tap 230 is positioned such that a first threadflight contacts pedicle 164, a first measurement of the position of thetap relative to a top of dilator 302 using indicia 240 may be noted. Tap230 may be rotated to form a threaded passage through pedicle 164 andinto vertebral body 166 to a desired depth. In some embodiments, alength of the threaded portion of tap 230 may be used to determine adepth of a threaded passage formed in a bone. For a threaded portion ofa known length (e.g., 30 mm, 45 mm, 60 mm), a scaled image (e.g., X-rayimage) of a depth of the threaded portion in a bone monitored duringtapping may allow a medical practitioner to determine the depth of thethreaded passage. In some embodiments, tap 230 may form threads of majordiameter about 0.5 mm smaller than a major diameter of threads of a bonefastener to be inserted into the threaded passage.

FIG. 66E depicts a position of tap 230 after a threaded passage of adesired length has been formed in pedicle 164 and vertebral body 166.Care should be exercised to ensure that guide wire 218 is not bent orkinked during the tapping process. The position of tap 230 relative tothe end of guide wire 218 may be monitored to ensure that guide wire 218is not dislodged or removed from the vertebra. In some embodiments, aposition of tap 230 may be monitored using fluoroscopic imaging.

After a threaded passage of a desired length has been formed in pedicle164 and vertebral body 166, a second measurement of the position of tap230 relative to a top of dilator 302 using indicia 240 may be noted. Alength of a threaded member may be determined by taking a differencebetween the first and second measurements. In some embodiments, anestimate of length may be derived based upon fluoroscopic images and aknown length of the tap that is visibly recognizable in the fluoroscopicimages. Tap 230 may be removed from vertebral body 166 and pedicle 164by rotating the tap out of the vertebral body and the pedicle. Handle236 may be removed from a blade portion of tap 230. The blade portion oftap 230 may be removed from guide wire 218 with control of the guidewire initially maintained from above the tap and then from below thetap. Care may be taken when tap 230 is removed to maintain guide wire218 in position and to avoid damage of the guide wire. FIG. 66F depictsdilator 302 and guide wire 218 after removal of the tap.

A bone fastener assembly with a bone fastener of an appropriate lengthmay be selected for insertion in a patient. The size of the bonefastener may be verified with measurement indicia in an instrumentationset. In some embodiments, measurement indicia may be etched or printedon a portion of an instrumentation set. For example, the chosen bonefastener embodiment may be placed over the outline of a bone fastenerembodiment printed on a tray of the instrumentation set.

The chosen bone fastener assembly may be attached to a detachablemember. In an embodiment, a bone fastener assembly may be rotated on aflange of a detachable member. Movable members of the detachable membermay be extended into indentations in a collar of the bone fastenerassembly. A driver may be used to extend the movable members to couplewith the collar. When the bone fastener assembly is coupled to thedetachable member, a drive portion of a fastener driver may be coupledto a tool portion of the bone fastener. A shaft of the fastener drivermay be positioned in the passage of the detachable member. A removablehandle may be attached to the shaft of the fastener driver. Thedetachable member, collar, and bone fastener may be substantiallyco-axial when the fastener driver is positioned in the detachablemember. In some embodiments, the removable handle may be attached to theshaft of the fastener driver after the bone fastener, collar, detachablemember, and fastener driver combination is positioned down a guide wirethrough a dilator and against a pedicle.

FIGS. 67A-67D depict portions of a procedure for inserting a bonefastener assembly into a patient. Driver 292 (coupled to the bonefastener), and sleeve 244 (coupled to the collar of the bone fastenerassembly) may be inserted along guide wire 218 into dilator 302. Forspinal stabilization procedures using four successively sized dilators,dilator 302 may be fourth dilator 302D. Guide wire 218 represents thetrajectory that a bone fastener or bone fastener assembly may followtoward pedicle 164 during insertion of a spinal stabilization system. Insome embodiments, tissue surrounding the incision may be pulled and/orstretched to allow a desired angular orientation of the bone fastenerassembly relative to pedicle 164. FIG. 67A depicts driver 292 and sleeve244 positioned in dilator 302. After insertion of the bone fastenerassembly, sleeve 244, and driver 292 in dilator 302, the driver may berotated to thread the bone fastener into pedicle 164 and vertebral body166. The bone fastener may be advanced into the pedicle underfluoroscopic guidance to inhibit breaching of the pedicle walls. Whenthe tip of the bone fastener advances beyond the posterior margin ofvertebral body 166, guide wire 218 may be removed to inhibit inadvertentbending of the guide wire or unwanted advancement of the guide wire.

The bone fastener may be advanced to bring the collar down snug to thefacet joint. The bone fastener may then be backed off about a quarter ofa turn. Backing the fastener off about a quarter of a turn may allow forfull motion of the collar relative to the bone fastener. FIG. 67Bdepicts driver 292 after the bone fastener has been advanced to thedesired depth. After the bone fastener has been advanced to the desireddepth, driver 292 may be removed from the head of the bone fastener andfrom dilator 302. FIG. 67C depicts dilator 302 and sleeve 244 afterremoval of the driver. After removal of the driver, dilator 302 may beremoved from the patient. FIG. 67D depicts collar 112 of bone fastenerassembly and sleeve 244 after removal of the dilator.

After the bone fastener has been secured to the vertebra and the driverhas been removed from the sleeve, the polyaxial nature of the collar mayallow angulation of the sleeve relative to the bone fastener. Tissuesurrounding the incision may be released such that the sleeve is angledtoward a central location between vertebrae to be stabilized. The sleevemay be moved to facilitate positioning of instruments and/or tofacilitate access to the adjacent vertebra that is to be stabilized. Forexample, the sleeve may be tilted towards the adjacent pedicle so thatadditional length of an opening in the patient is not needed. Thechannel in the sleeve may be turned toward the adjacent pedicle that isto be stabilized with the spinal stabilization system being formed.

A plane of dilated tissue may be created between a first pedicle and asecond pedicle to be stabilized with a spinal stabilization system. Abone fastener assembly and a sleeve may be coupled to the first pedicle.The second pedicle may be adjacent to the first pedicle. In anembodiment, a tissue wedge may be placed in the sleeve coupled to thefirst pedicle such that the distal end of the tissue wedge contacts thehead of the bone fastener. The proximal end of the sleeve coupled to thefirst pedicle may be held such that tissue around the incision is notpulled or stretched. The tissue wedge may be wanded through the channelin the sleeve and the slot in the collar toward the target location atthe second pedicle, thereby creating a plane in muscle and other tissuebetween the head of the installed bone fastener and the target locationof a second bone fastener. In some embodiments, a tissue wedge may bepivoted about an inside proximal edge of the sleeve such that the distalend of the tissue wedge bluntly splits the muscle and fascia alongfibers and create a tissue plane between the two pedicles. The wandingaction may be repeated more than once (e.g., two or three times) tocreate a good working plane and displace unwanted tissue from the plane.The wanding may create a tissue plane. In some embodiments, the tissueplane may be substantially trapezoidal In certain embodiments, a tissueplane may be created before a bone fastener assembly is inserted into avertebra.

FIGS. 68A-D depict some stages during use of a tissue wedge to form atissue plane between a sleeve in a first pedicle and a target locationat a second pedicle. FIG. 68A depicts tissue wedge 308 aligned abovepedicle 164A in sleeve 244. With a portion of tissue wedge 308 heldproximate to the proximal end of sleeve 244 or resting on the proximalend of the sleeve, blade 312 of tissue wedge 308 may be moved throughsoft tissue from pedicle 164A toward pedicle 164B. FIG. 68B depictsdistal end of tissue wedge 308 positioned at pedicle 164B. After tissuewedge 308 contacts pedicle 164B, handle 310 may be moved toward pedicle164B (i.e., away from sleeve 244) to further separate soft tissue in aplane between the pedicles. FIG. 68C depicts tissue wedge 308 afterhandle 310 has been angled away from sleeve 244. An initial plane may becreated by wanding tissue wedge from pedicle 164A to pedicle 164B.Tissue wedge 308 may be similarly wanded back to pedicle 164A to furtherestablish the plane. FIG. 68D depicts tissue wedge 308 realigned insleeve 244 after the plane has been established with a back-and-forthmotion. In some embodiments, handle 310 may be maintained proximatesleeve 244 to minimize the area of the tissue plane.

A tissue plane may be made in a variety of shapes including, but notlimited to, substantially trapezoidal, substantially rhomboidal, andsubstantially triangular. A tissue plane with a substantially geometricshape may have the basic geometric shape with, for example, slightlycurved edges and/or slightly rounded corners or apices. In someembodiments, a sleeve length may be chosen to reduce a size of a tissueplane that needs to be formed between pedicles. In certain embodiments,creating a trapezoidal tissue plane may reduce the invasiveness of aprocedure Limiting the area of the plane may promote a faster recoverytime and/or may reduce an amount of post-operative pain experienced bythe patient.

In an embodiment, a tissue wedge may be coupled to a portion of a sleeveto facilitate creation of a tissue plane. FIG. 69 depicts tissue wedge308 with blade 312 pivotally coupled to a proximal extension of sleeve244. Tissue wedge 308 may be initially positioned in sleeve 244 with adistal end of blade 312 proximate pedicle 164A. Handle 310 may bepivoted toward pedicle 164A to allow wanding of blade 312 towardsadjacent pedicle 164B. If needed, cutting edge 318 may be used to severfascia that inhibits passage of blade 312. Sleeve 244 may be pivoted inconjunction with rotation of collar 112. In another embodiment, sleeve244 may be extendable (e.g., telescopic) such that a pivot point may beadvanced in the direction of pedicle 164B during wanding. The extendableportion of the sleeve may be selectively lockable using a variety oflocking mechanisms including, but not limited to, a setscrew, a clip, adetent, or a pin.

In an embodiment, two pedicles may be targeted and bone fastenerassemblies anchored in both pedicles before creation of a tissue plane.A tissue wedge may be inserted at either of the pedicles. In someembodiments, the sleeves may be coupled to each other at proximal endsof the sleeves. The tissue wedge may be coupled to a sleeve and thesleeve may be used as an anchor during wanding. Insertion of anelongated member into collars of bone fastener assemblies, however, mayrequire cutting of some tissue between the two sleeves.

Other procedures may be used to create a tissue plane. For example,before targeting pedicle locations (i.e., before bone fastenerinsertion), a tissue wedge may be worked downward from an incision tocreate a tissue plane. Alternatively, a scalpel may be used to cut fromthe surface of the body to vertebral bone. Extensive use of a scalpel,however, may remove benefits of a minimally invasive procedure.

In an embodiment, a targeting needle may be passed through the tissue tocreate a tissue plane for insertion of an elongated member. As depictedin FIG. 70A, targeting needle 198 may be placed in sleeve 244A coupledto pedicle 164A. Sleeve 244A may be rotated such that channel 248 isdirected toward pedicle 164B. In some embodiments, a handle portion oftargeting needle 198 may be positioned over pedicle 164B, as depicted inFIG. 70B. The shaft of targeting needle 198 may be wanded from sleeve244A (e.g., from a center of sleeve 244A) in pedicle 164A to a targetlocation in pedicle 164B to separate the soft tissue in a plane betweenthe pedicles. FIG. 70C depicts a distal end of targeting needle 198positioned proximate pedicle 164B. Targeting needle 198 may be movedback and forth to establish the plane. After targeting needle 198contacts pedicle 164B and the plane is established, a bone fastenerassembly may be inserted in pedicle 164B using a procedure similar tothe procedure used to place a bone fastener assembly in an adjacentpedicle. FIG. 70D depicts sleeves 244A and 244B located proximatepedicles 164A and 164B, respectively.

Once a well-defined tissue plane has been formed, a targeting needle maybe passed down a first sleeve coupled to a first vertebra and thenwanded along the formed plane over to a target location at a secondpedicle. The target location at the second pedicle may befluoroscopically confirmed. A bone fastener assembly coupled to a sleevemay be secured in the second pedicle using a procedure similar to theprocedure used to insert a bone fastener assembly in a first pedicle.FIG. 71 depicts substantially trapezoidal tissue plane 378 betweensleeves 24 coupled to adjacent vertebral bodies 166. Sleeves 244 touchat incision 375 and cross above body surface 376, such that a length ofthe incision and/or an area of tissue plane 378 may be advantageouslysmall. Substantially trapezoidal tissue plane 378 may have a dimensionat body surface 376 equal to a length of the incision. Sides ofsubstantially trapezoidal tissue plane 378 may be define by surfaces ofsleeves 244. Opposite the body surface 376, substantially trapezoidaltissue plane 378 may extend between collars 112. In some embodiments,the edge of substantially trapezoidal tissue plane 378 closest vertebralbodies 166 may be substantially straight. In some embodiments, the edgeof substantially trapezoidal tissue plane 378 closest vertebral bodies166 may be curved to match a contour of bone between the vertebralbodies.

With bone fastener assemblies secured in the vertebral bodies, sleevescoupled to the bone fastener assemblies may be oriented to facilitateinsertion of an elongated member in the sleeves. In some embodiments,sleeves may serve as tissue retractors during a spinal stabilizationprocedure. Angular motion of a collar may be limited by a range ofmotion allowed between the collar and the bone fastener that the collaris anchored to. Angular motion of a collar may be limited by patientanatomy. Angular motion or orientation of one collar (i.e., sleeve),however, may not depend upon a position of another collar (i.e.,sleeve). In some embodiments, channel openings in the sleeves may faceeach other. In other embodiments, channel openings in the sleeves may beangled relative to each other in various arrangements. A distancebetween the sleeves may be estimated using an estimating tool. Thedistance between the sleeves may be used to select a length of anelongated member needed to couple the collars.

In an embodiment, flexible arms of estimating tool 320 depicted in FIG.54 may be positioned in sleeves. With the activator disengaged, theestimating tool may be advanced toward the pedicles until the arms ormembers rest on the collars or bone fasteners of the bone fastenerassemblies. The activator may be engaged. When the arms are withdrawnfrom the sleeves, a biasing element may allow the arms to extend to thelength indicative of the distance between bone fastener assemblies. Anelongated member length may be selected by measuring a distance betweenthe members of the estimating tool. The measured distance may beincreased by an amount to allow the elongated member to extend beyondthe collars after curvature and/or insertion. In an embodiment, about 5mm to about 30 mm (e.g., about 15 mm) may be added to the measureddistance. In some embodiments, a desired length of an elongated membermay be a length that allows the elongated member to extend from eachcollar by about 2 mm or about 3 mm. In certain embodiments, ends of anelongated member may be flush with the outer surface of one or morecollars.

In an embodiment, an elongated member of desired length may be chosen byestimating a distance between the sleeves without the use of anestimating tool. The sleeves may be positioned as desired (e.g.,substantially parallel to each other). A distance between the mostdistant outer edges of the sleeves may be estimated. The estimateddistance may be increased by an amount to allow the elongated member toextend beyond the collars after insertion. In some embodiments, fromabout 1 mm to about 20 mm may be added to the estimated distance. Insome embodiments, a desired length of elongated member may be a lengththat allows the elongated member to extend from each collar by about 2mm.

An elongated member may be cut to length and contoured as desired. Forexample, a medical practitioner may use experience and judgment todetermine curvature of an elongated member for a patient. A desiredcurvature for the elongated member may be determined using fluoroscopicimaging. In some embodiments, a curvature of the elongated member may bechosen such that, when the elongated member is secured to the collars ofthe bone fastener assemblies, sleeves coupled to the bone fastenerassemblies cross at a surface of the skin. Crossing of the sleeves at asurface of the skin allows the medical practitioner to minimize traumato a patient by minimizing incision length and tissue plane area. Theelongated member may be bent or shaped with a tool (e.g., a rod bender)to allow insertion of the elongated member through channels of sleeveswith various spatial locations and/or various angular orientations.

Elongated members may have shapes including, but not limited to,straight, bent, curved, s-shaped, and z-shaped. FIG. 72 depicts anembodiment of S-shaped elongated member 104. FIG. 73 depicts anembodiment of angled elongated member 104. FIG. 74 depicts an embodimentof bent elongated member 104. FIG. 75 depicts an embodiment of straightelongated member 104. In some embodiments, elongated members 104 mayhave a substantially circular longitudinal cross section. In certainembodiments, elongated members 104 may have other cross-sectional shapesincluding, but not limited to, regular shapes (oval, rectangular,rhomboidal, square) and irregular shapes. An instrumentation kit for aspinal stabilization system may include straight rods and/or pre-shapedrods. Straight rods and/or pre-shaped rods may be contoured toaccommodate patient anatomy if needed during the surgical procedure.

Channels of the sleeves and slots of the collars may be oriented byrotating the sleeves to accommodate insertion and seating of theelongated member. In certain embodiments, a channel opening in a sleevemay be non-linear (e.g., bent, curved, or angled) to allow portions ofthe spine to be selectively stabilized. Sleeve orientation and/or designmay be chosen to allow compression, distraction, and/or reduction ofvertebrae. In some embodiments, there may be no constraints governingrelative location and/or orientation of the sleeves. Sleeves may beforced apart or angled toward each other or away from each other toaccommodate insertion of the elongated member.

Prior to insertion of the elongated member, the tissue wedge ortargeting needle may be used to wand between the bone fasteners toensure a clean plane between the bone fasteners. An end of the elongatedmember may be inserted at an angle or substantially longitudinally in apassage and/or channel of a sleeve coupled to a bone fastener assembly.Inserting the elongated member at an angle or substantiallylongitudinally allows the length of the incision and/or the area of thetissue plane to remain advantageously small. In some embodiments,sleeves coupled to anchored bone fastener assemblies may remainessentially unconstrained relative to each other during insertion of theelongated member. In certain embodiments, angular orientation of thecollars may determine a trajectory of the elongated member down thesleeves and into collars of the bone fastener assemblies. Inserting theelongated member down two or more sleeves and through an open path(i.e., the tissue plane) may allow a medical practitioner to avoidsurgical difficulties associated with anatomical abnormalities and/ormisalignment of system components (e.g., in multi-level stabilizationprocedures).

Insertion of the elongated member may not be visualized subcutaneously.Therefore, a positioning tool may be used to guide the elongated memberdown the sleeves into slots in the collars. A distal portion of thepositioning tool may be contoured. The contour may allow for somerotation of the elongated member. With slight pressure, the elongatedmember may be rotated subcutaneously into a substantially horizontalposition and seated in the collars. The positioning tool may be heldfirmly while still allowing a rocking movement between the elongatedmember and the distal end of the positioning tool. Movement of theelongated member may allow the elongated member to be maneuvered downthe sleeves and into the collars.

FIG. 76A depicts insertion of a first end of elongated member 104 in anopening of channel 248A of sleeve 244A. In an embodiment, elongatedmember 104 may be positioned between grasping member 342 and distal end344 of the inner shaft of positioning tool 334, as shown in FIG. 76B.The elongated member may be held between grasping member 342 and distalend 344 of the inner shaft of positioning tool 334 with pressure appliedto a proximal end of the inner shaft. As the first end of elongatedmember 104 is moved along the length of sleeve 244A toward collar 112A)a second end of the elongated member may be inserted in channel 248B ofsleeve 244B. Channels in sleeves 244A and 244B may include groovesopposite channel openings to engage ends of elongated member 104 and/orto guide the elongated member along the lengths of the sleevesPositioning tool 334 may be used to guide the elongated member along thelength of the sleeves through the plane in the soft tissue.

Slots in collars 112A, 112B may be aligned with channels 248A, 248B ofsleeves 244A, 244B, respectively, to allow elongated member 104 to bepositioned in the collars. Positioning tool 334 may be used to angle theelongated member through slot 150A such that an end of the elongatedmember protrudes through collar 112A away from collar 112B. With one endof elongated member 104 extending through slot 150A in collar 112A,positioning tool 334 may be used to guide the other end of the elongatedmember the remaining distance down second sleeve 244B. Positioning tool334 may then be used to seat the second end of elongated member 104 incollar 112B and translate the elongated member to a desired locationrelative to the collars. The distal end of the positioning tool innershaft may be contoured (e.g., curved and/or grooved) to allow somemotion (e.g., rocking) of elongated member 104 while the elongatedmember is coaxed into position and/or rotated subcutaneously with thepositioning tool. Pressure may be applied to inner shaft 340 to seatelongated member 104 in the slots of the collars. FIG. 76C depictselongated member 104 seated in collars 112A, 112B.

In some embodiments, a seater may be used to seat the elongated memberin the collars. FIG. 76D depicts seater 348 positioned in sleeve 244B.In certain embodiments, seater 348 may be used to push elongated member104 into slots in collar 112A and/or 112B while the positioning tool isused to maneuver the elongated member into place. Once the elongatedmember is positioned in the collars, fluoroscopic confirmation mayensure that the elongated member is inserted fully into each collar.Prior to securing the elongated member to bone fastener assemblies withclosure members, the elongated member may be gripped firmly with thepositioning tool and persuaded cephalad or caudad as needed. With theelongated member seated in the collars, orientation of the sleeves maybe constrained relative to each other.

After the elongated member is seated in the collars, additionalfluoroscopic confirmation of elongated member positioning may beobtained. With the elongated member satisfactorily positioned, theelongated member may be secured in place with closure members. FIG. 60Adepicts closure member 106 coupled to driver 354. Driver 354 ispositioned for insertion into sleeve 244. A counter torque wrench may becoupled to the sleeve or to the elongated member. After insertion ofdriver 354 in sleeve 244, closure member 106 may be positioned proximatecollar 112. With driver 354 positioned in sleeve 244, as shown in FIG.60B, the driver may be rotated to advance the closure member in collar112. To ensure alignment of thread of closure member with thread ofcollar, the driver may initially be rotated in a direction that wouldresult in removal of the closure member from the collar. When the userof the driver feels engagement of threading of the closure member withthreading of the collar, the user may reverse the direction of rotationof the driver to secure the closure member to the driver. The closuremember may secure the elongated member to the collar. Sleeve 244A mayserve as a coaxial guide to inhibit cross-threading during insertion ofclosure members 106. When the closure members are snug and elongatedmember 104 is secured, collars 112 are angled such that slots in thecollars are substantially perpendicular to the elongated member. Driver354 may be disengaged from the closure member and removed from sleeve244. In some embodiments, driver 354 may be used to shear off a toolportion of a secured closure member. In certain embodiments, a couplingportion of driver 354 may capture a sheared tool portion from a closuremember.

Torque required to shear off the tool portion of a closure member may bea source of pain and/or injury to a patient. In some embodiments, sleeve244 may be held with a counter torque wrench as the tool portion of asecured closure member is sheared off. In an embodiment, about 90 in-lbsof torque may be required to shear off the tool portion of a closuremember. A counter torque wrench may inhibit or reduce transfer of torqueto the patient's spine. FIG. 61 depicts an embodiment of counter torquewrench 364 used above the skin to inhibit application of torque to apatient's spine during shearing of a tool portion of a secured closuremember. Sleeve 244 may fit in opening 366 of counter torque wrench 364.Counter torque wrench 364 may be positioned near a proximal end ofsleeve 244 during use.

Force may be applied to counter torque wrench 364 in a directionopposite to rotational force applied to driver 354 to shear off a toolportion of closure member 106. Thus, the tool portion of closure member106 may be sheared off with force exerted above the incision of apatient. In some embodiments, a collar of a bone fastener assembly maybe designed such that a proximal portion of the collar may be shearedoff with force exerted above the incision of a patient. In someembodiments, closure member 106 may be designed (e.g., with a solidcentral core) such that the torque required to shear off the toolportion does not adversely affect the body of the closure member or thecoupling between the closure member and the collar. Opening 366 intorque wrench 364 may be of any shape to accommodate a cross-sectionalshape of sleeve 244.

In some embodiments, counter torque wrench 368 shown in FIG. 63 may beused to inhibit application of torque to a patient's spine. Countertorque wrench sleeve 370 may be inserted through the opening in the bodyover sleeve 244. Counter torque wrench sleeve 370 may be advanced towardthe spine until elongated member 104 is seated in groove 374 of thecounter torque wrench sleeve. Force may be applied to counter torquewrench 368 in a direction opposite to rotational force applied to adriver used to shear off a tool portion of a secured closure member.

Coupling failure between a collar and a closure member of a bonefastener assembly may be a concern during surgery. If failure occurswhile locking down an elongated member to a bone fastener assembly in asingle- or multi-level system, the failure may require removal of one ormore locked closure members and the elongated member to extract a failedbone fastener assembly. Coupling failure may occur during application ofother loads, such as loads used to achieve reduction with a spinalstabilization system.

FIG. 77 depicts a distal portion of driver 380 that may be used toremove closure member 106 depicted in FIGS. 14 and 15. A distal end ofdriver 380 may include two prongs designed to fit in removal openings174 of closure member 106. Driver 380 may be inserted in a sleeve toengage a closure member. A handle of driver 380 may allow a medicalpractitioner to apply force in a rotational direction necessary toremove the closure member. In some embodiments, a counter torque wrenchmay be used to inhibit application of torque to the patient's spineduring removal of a closure member. The closure member may be removedand replaced as necessary.

After a closure member is successfully secured to a collar and a toolportion of the closure member has been sheared off, the driver may beremoved from the sleeve coupled to the anchored bone fastener assembly.FIG. 78A depicts an assembled spinal stabilization system followingremoval of driver 354. Key 262, shown in FIG. 78B, may be used to rotatemovable members in sleeves 244A, 244B. Rotation of movable members insleeves 244A, 244B may release the movable members from the collars.Thus, sleeves 244A, 244B may be uncoupled from the collars above theincision. FIG. 78C depicts assembled spinal stabilization system 100following removal of sleeve 244A. FIG. 78D depicts assembled spinalstabilization system 100 coupled to adjacent pedicles following removalof sleeve 244B.

A spinal stabilization system may be used to stabilize two or morevertebral levels (i.e., at least three adjacent vertebrae). In anembodiment, an incision may be made in the skin between the outermostvertebrae to be stabilized. A first bone fastener assembly may becoupled to a first sleeve. The first bone fastener may be threaded intoa first pedicle at a target location such that the first sleeve extendsabove the body surface. The first sleeve may rotate about the head ofthe first bone fastener. A tissue plane may be created between a channelopening in the first sleeve and a target location at a second pedicle.In an embodiment, the second pedicle may be adjacent to the firstpedicle. A second bone fastener assembly may be coupled to a secondsleeve and threaded into the second pedicle through the incision.Another tissue plane may be created between the first sleeve or thesecond sleeve and a target location in a third pedicle. The thirdpedicle may be adjacent to the first pedicle and/or the second pedicle.A third bone fastener assembly may be coupled to a third sleeve andthreaded into the third pedicle through the incision.

In an embodiment of a method for a two-level spinal stabilizationprocedure, an incision may be made above a target location in a middlepedicle. A first bone fastener may be anchored to the middle pedicle.After the first bone fastener is secured, second and third bonefasteners may be coupled to outer pedicles as desired by pulling and/orstretching tissue surrounding the incision to allow access to the outerpedicles.

Channel openings in sleeves coupled to three bone fastener assembliesmay be oriented to allow insertion of an elongated member to achievetwo-level spinal stabilization. FIGS. 79A-79E depict insertion andseating of an elongated member in a two-level spinal stabilizationsystem. Use of a rod positioner and/or seater is implied but not shownin FIGS. 79A-79E. FIG. 79A depicts insertion of a first portion ofelongated member 104 through channel 248′ of multi-channel sleeve 244and into channel 248 of sleeve 244B. As the first portion of elongatedmember 104 is moved down the length of channels 248, 248′ toward collars112, 112′, a second portion of the elongated member may be inserted inchannel 248 of sleeve 244A. In some embodiments, elongated member 104may be moved down channels 248, 248′ using a positioning tool. Aselongated member 104 is advanced toward collars 112, 112′, the elongatedmember may pass through an opening in the skin and into the tissueplane. FIG. 798 depicts elongated member 104 in channels 248, 248′.Channels 248 in sleeves 244A, 244B may include grooves to engage ends ofelongated member 104 and/or to guide the elongated member down thelengths of the sleeves. In certain embodiments, channel openings may becurved or angled to accommodate various elongated member configurations.

FIG. 79C depicts elongated member 104 engaged in channels 248, 248′. Aselongated member 104 is advanced toward collars 112, 112′, a first endof the elongated member may emerge through slot 150 in collar 112coupled to sleeve 244B. FIG. 79D depicts elongated member 104 after theelongated member has emerged through slot 150 in collar 112 coupled tosleeve 244B. In some embodiments, a seater may be used to positionelongated member 104 in collars 112, 112′. FIG. 79E depicts elongatedmember 104 seated in collars 112, 112′.

FIGS. 80A-80C depict perspective views of various orientations sleeves244 may assume relative to bone fasteners 108, 108′. In two-level andmulti-level spinal stabilization systems, an orientation of a sleevecoupled to an anchored bone fastener assembly is not constrained by anorientation of one or more other collars coupled to adjacent bonefastener assemblies. FIGS. 80A-80C also depict various orientations thatbone fasteners 108, 108′ may assume relative to each other. Bonefasteners 108, 108′ may be offset from each other (i.e., non-planar)and/or be inserted in pedicles at opposing angles. The range of possibleorientations of bone fasteners in pedicles may allow a spinalstabilization system to securely conform to a patient's spine.

After an elongated member has been positioned and seated in collars asdesired, closure members may be used to secure the elongated member tothe collars. One or more counter torque wrenches may be used duringshearing of the tool portions of the closure members. In an embodiment,counter torque wrench 364, depicted in FIG. 61, may be used with sleeves244A, 244B. Counter torque wrench 368, depicted in FIG. 62, may be usedwith multi-channel sleeves and/or single-channel sleeves.

In certain embodiments, an external frame may be used to impose adesired constraint on one or more sleeves. For example, an externalframe may hold one or more sleeves in a particular location and/ororientation such that a desired relative positioning of vertebrae may beachieved. An external frame may be used to impose a distance and/orangle between sleeves to achieve distraction or compression ofvertebrae. Reduction of vertebrae may be achieved when an external frameis used to adjust a relative height of the sleeves.

In some embodiments, a spinal stabilization system may be inserted usingan invasive procedure. Since insertion of a spinal stabilization systemin an invasive procedure may be visualized, cannulated components (e.g.,bone fasteners) and/or instruments (e.g., detachable members) may not beneeded for the invasive (i.e., open) procedure. Thus, a bone fastenerused in an invasive procedure may differ from a bone fastener used in aminimally invasive procedure. FIG. 81 depicts a perspective view of anembodiment of bone fastener 108 that may be used in an invasiveprocedure.

Bone fastener 108 may include shank 116, head 118, and neck 120. Shank116 may include threading 122. In some embodiments, threading 122 mayinclude self-tapping start 124. Self-tapping start 124 may facilitateinsertion of bone fastener 108 into vertebral bone. Head 118 of bonefastener 108 may include various configurations to engage a driver thatinserts the bone fastener into a vertebra. In certain embodiments, thedriver may also be used to remove an installed bone fastener from avertebra.

In some embodiments, head 118 may include one or more tool portions 126.Tool portions 126 may be recesses and/or protrusions designed to engagea portion of the driver. Driver 380 depicted in FIG. 77 may be used toengage bone fastener 108 with tool portions 126 as depicted in FIG. 81.Head 118 of bone fastener 108 may include one or more splines. In someembodiments, bone fastener 108 may be used with a collar, a ring, and/ora closure member described for use with a cannulated bone fastener. Incertain embodiments, bone fasteners with closed collars may be used inan invasive spinal stabilization procedure. In certain embodiments,fixed bone fasteners (e.g., open fixed bone fasteners) may be used in aninvasive spinal stabilization procedure.

In some embodiments, tools used in an invasive procedure may be similarto tools used in a minimally invasive procedure. In certain embodiments,methods of installing a spinal stabilization system in an invasiveprocedure may be similar to methods of installing a spinal stabilizationsystem in a minimally invasive procedure.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

1. A system for performing spine surgery, said system comprising: afirst bone screw configured to be screwed into a first vertebra; a firstcollar coupled to the first bone screw, said first collar comprising afirst slot; a second bone screw configured to be screwed into a secondvertebra; a second collar coupled to the second bone screw, said secondcollar comprising a second slot; a rod, said rod having a width sized tofit within the first slot and the second slot; a first sleeve comprisinga first passage, said first passage extending longitudinally from afirst end of the first sleeve to a second end of the first sleeve; afirst closure member configured to be secured to the first collar forsecuring the rod within the first slot; a second sleeve comprising asecond passage, said second passage extending longitudinally from afirst end of the second sleeve to a second end of the second sleeve; asecond closure member configured to be secured to the second collar forsecuring the rod within the second slot; wherein the first sleeve andthe first collar comprise a first coupling system for coupling the firstcollar to the first sleeve, said first coupling system configured toprovide a detachable mechanical coupling between an outer surface of thefirst collar and an inner surface of the first sleeve; wherein thesecond sleeve and the second collar comprise a second coupling systemfor coupling the second collar to the second sleeve, said secondcoupling system configured to provide a detachable mechanical couplingbetween an outer surface of the second collar and an inner surface ofthe second sleeve; wherein the first passage is sized to permit thepassage of a tool for securing the first closure member to the firstcollar; and wherein the second passage is sized to permit the passage ofa tool for securing the second closure member to the second collar. 2.The system of claim 1, wherein the first coupling system comprises aprotrusion on the outer surface of the first collar.
 3. The system ofclaim 2, wherein the first coupling system further comprises a recess inthe inner surface of the first sleeve, said recess configured forcomplimentary engagement with the protrusion.
 4. The system of claim 3,wherein the protrusion is a collar flange, and wherein the recess is asleeve flange.
 5. The system of claim 1, wherein the first couplingsystem comprises a protrusion on the inner surface of the first sleeve.6. The system of claim 5, wherein the first coupling system furthercomprises a recess on the outer surface of the first collar, said recessconfigured for complimentary engagement with the protrusion.
 7. Thesystem of claim 6, wherein the protrusion is a sleeve flange, andwherein the recess is a collar flange.
 8. The system of claim 1, whereinthe first sleeve is configured to be coupled to the first collar at alocation above the rod seated within the first slot.
 9. The system ofclaim 1, wherein the first sleeve is configured to be detachably coupledwith the first collar by rotating the first sleeve onto the firstcollar.
 10. The system of claim 9, wherein rotating the first sleeveonto the first collar moves a first sleeve protrusion into a firstcollar recess.
 11. The system of claim 1, wherein the first sleevecomprises first and second arms and the first sleeve is configured to bedetachably coupled with the first collar by deflecting the first andsecond arms outwards to receive the first collar.
 12. The system ofclaim 1, wherein the first sleeve comprises a first inner sleeve and afirst outer sleeve, a distal portion of the first inner sleeveconfigured to engage the first collar, the first outer sleeve configuredto extend over the first inner sleeve and at least a portion of thefirst collar.
 13. The system of claim 12, wherein the first couplingsystem includes threading on an outer surface of the first inner sleeve.14. The system of claim 13, wherein the first coupling system furthercomprises threading on an inner surface of the first outer sleeve, saidthreading on the outer surface of the first inner sleeve configured forcomplimentary engagement with the threading on the inner surface of thefirst outer sleeve.
 15. The system of claim 1, wherein the firstcoupling system comprises an interference fit between the first collarand the first sleeve.
 16. The system of claim 1, wherein the firstcoupling system comprises a frictional fit between the first collar andthe first sleeve.
 17. The system of claim 1, wherein the first couplingsystem comprises a keyway connection between the first collar and thefirst sleeve.
 18. The system of claim 1, wherein the first couplingsystem comprises a notch on an outer surface of the first collar. 19.The system of claim 18, wherein the first coupling system furthercomprises an extension on the first sleeve configured to extend into thenotch.
 20. The system of claim 1, further comprising: a third bone screwconfigured to be screwed into a third vertebra; a third collar coupledto the third bone screw, said third collar comprising a third slot, therod having a width sized to fit within the third slot; a third sleevecomprising a third passage, said third passage extending longitudinallyfrom a first end of the third sleeve to a second end of the thirdsleeve; a third closure member configured to be secured to the thirdcollar for securing the rod within the third slot; wherein the thirdsleeve and the third collar comprise a third coupling system forcoupling the third collar to the third sleeve, said third couplingsystem configured to provide a detachable mechanical coupling between anouter surface of the third collar and an inner surface of the thirdsleeve; and wherein the third passage is sized to permit the passage ofa tool for securing the second closure member to the second collar.